feat(memory): add database schema and storage layer (Issue #88)

Add SQLAlchemy models for the Agent Memory System:
- WorkingMemory: Key-value storage with TTL for active sessions
- Episode: Experiential memories from task executions
- Fact: Semantic knowledge triples with confidence scores
- Procedure: Learned skills and procedures with success tracking
- MemoryConsolidationLog: Tracks consolidation jobs between memory tiers

Create enums for memory system:
- ScopeType: global, project, agent_type, agent_instance, session
- EpisodeOutcome: success, failure, partial
- ConsolidationType: working_to_episodic, episodic_to_semantic, etc.
- ConsolidationStatus: pending, running, completed, failed

Add Alembic migration (0005) for all memory tables with:
- Foreign key relationships to projects, agent_instances, agent_types
- Comprehensive indexes for query patterns
- Unique constraints for key lookups and triple uniqueness
- Vector embedding column placeholders (Text fallback until pgvector enabled)

Fix timezone-naive datetime.now() in types.py TaskState (review feedback)

Includes 30 unit tests for models and enums.

Closes #88

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/tests/unit/models/__init__.py

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+# tests/unit/models/__init__.py
+"""Unit tests for database models."""

backend/tests/unit/models/memory/__init__.py

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+# tests/unit/models/memory/__init__.py
+"""Unit tests for memory database models."""

backend/tests/unit/models/memory/test_enums.py

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+# tests/unit/models/memory/test_enums.py
+"""Unit tests for memory model enums."""
+
+from app.models.memory.enums import (
+    ConsolidationStatus,
+    ConsolidationType,
+    EpisodeOutcome,
+    ScopeType,
+)
+
+
+class TestScopeType:
+    """Tests for ScopeType enum."""
+
+    def test_all_values_exist(self) -> None:
+        """Test all expected scope types exist."""
+        assert ScopeType.GLOBAL.value == "global"
+        assert ScopeType.PROJECT.value == "project"
+        assert ScopeType.AGENT_TYPE.value == "agent_type"
+        assert ScopeType.AGENT_INSTANCE.value == "agent_instance"
+        assert ScopeType.SESSION.value == "session"
+
+    def test_scope_count(self) -> None:
+        """Test we have exactly 5 scope types."""
+        assert len(ScopeType) == 5
+
+
+class TestEpisodeOutcome:
+    """Tests for EpisodeOutcome enum."""
+
+    def test_all_values_exist(self) -> None:
+        """Test all expected outcome values exist."""
+        assert EpisodeOutcome.SUCCESS.value == "success"
+        assert EpisodeOutcome.FAILURE.value == "failure"
+        assert EpisodeOutcome.PARTIAL.value == "partial"
+
+    def test_outcome_count(self) -> None:
+        """Test we have exactly 3 outcome types."""
+        assert len(EpisodeOutcome) == 3
+
+
+class TestConsolidationType:
+    """Tests for ConsolidationType enum."""
+
+    def test_all_values_exist(self) -> None:
+        """Test all expected consolidation types exist."""
+        assert ConsolidationType.WORKING_TO_EPISODIC.value == "working_to_episodic"
+        assert ConsolidationType.EPISODIC_TO_SEMANTIC.value == "episodic_to_semantic"
+        assert (
+            ConsolidationType.EPISODIC_TO_PROCEDURAL.value == "episodic_to_procedural"
+        )
+        assert ConsolidationType.PRUNING.value == "pruning"
+
+    def test_consolidation_count(self) -> None:
+        """Test we have exactly 4 consolidation types."""
+        assert len(ConsolidationType) == 4
+
+
+class TestConsolidationStatus:
+    """Tests for ConsolidationStatus enum."""
+
+    def test_all_values_exist(self) -> None:
+        """Test all expected status values exist."""
+        assert ConsolidationStatus.PENDING.value == "pending"
+        assert ConsolidationStatus.RUNNING.value == "running"
+        assert ConsolidationStatus.COMPLETED.value == "completed"
+        assert ConsolidationStatus.FAILED.value == "failed"
+
+    def test_status_count(self) -> None:
+        """Test we have exactly 4 status types."""
+        assert len(ConsolidationStatus) == 4

backend/tests/unit/models/memory/test_models.py

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+# tests/unit/models/memory/test_models.py
+"""Unit tests for memory database models."""
+
+from datetime import UTC, datetime, timedelta
+
+import pytest
+
+from app.models.memory import (
+    ConsolidationStatus,
+    ConsolidationType,
+    Episode,
+    EpisodeOutcome,
+    Fact,
+    MemoryConsolidationLog,
+    Procedure,
+    ScopeType,
+    WorkingMemory,
+)
+
+
+class TestWorkingMemoryModel:
+    """Tests for WorkingMemory model."""
+
+    def test_tablename(self) -> None:
+        """Test table name is correct."""
+        assert WorkingMemory.__tablename__ == "working_memory"
+
+    def test_has_required_columns(self) -> None:
+        """Test all required columns exist."""
+        columns = WorkingMemory.__table__.columns
+        assert "id" in columns
+        assert "scope_type" in columns
+        assert "scope_id" in columns
+        assert "key" in columns
+        assert "value" in columns
+        assert "expires_at" in columns
+        assert "created_at" in columns
+        assert "updated_at" in columns
+
+    def test_has_unique_constraint(self) -> None:
+        """Test unique constraint on scope+key."""
+        indexes = {idx.name: idx for idx in WorkingMemory.__table__.indexes}
+        assert "ix_working_memory_scope_key" in indexes
+        assert indexes["ix_working_memory_scope_key"].unique
+
+
+class TestEpisodeModel:
+    """Tests for Episode model."""
+
+    def test_tablename(self) -> None:
+        """Test table name is correct."""
+        assert Episode.__tablename__ == "episodes"
+
+    def test_has_required_columns(self) -> None:
+        """Test all required columns exist."""
+        columns = Episode.__table__.columns
+        required = [
+            "id",
+            "project_id",
+            "agent_instance_id",
+            "agent_type_id",
+            "session_id",
+            "task_type",
+            "task_description",
+            "actions",
+            "context_summary",
+            "outcome",
+            "outcome_details",
+            "duration_seconds",
+            "tokens_used",
+            "lessons_learned",
+            "importance_score",
+            "embedding",
+            "occurred_at",
+            "created_at",
+            "updated_at",
+        ]
+        for col in required:
+            assert col in columns, f"Missing column: {col}"
+
+    def test_has_foreign_keys(self) -> None:
+        """Test foreign key relationships exist."""
+        columns = Episode.__table__.columns
+        assert columns["project_id"].foreign_keys
+        assert columns["agent_instance_id"].foreign_keys
+        assert columns["agent_type_id"].foreign_keys
+
+    def test_has_relationships(self) -> None:
+        """Test ORM relationships exist."""
+        mapper = Episode.__mapper__
+        assert "project" in mapper.relationships
+        assert "agent_instance" in mapper.relationships
+        assert "agent_type" in mapper.relationships
+
+
+class TestFactModel:
+    """Tests for Fact model."""
+
+    def test_tablename(self) -> None:
+        """Test table name is correct."""
+        assert Fact.__tablename__ == "facts"
+
+    def test_has_required_columns(self) -> None:
+        """Test all required columns exist."""
+        columns = Fact.__table__.columns
+        required = [
+            "id",
+            "project_id",
+            "subject",
+            "predicate",
+            "object",
+            "confidence",
+            "source_episode_ids",
+            "first_learned",
+            "last_reinforced",
+            "reinforcement_count",
+            "embedding",
+            "created_at",
+            "updated_at",
+        ]
+        for col in required:
+            assert col in columns, f"Missing column: {col}"
+
+    def test_project_id_nullable(self) -> None:
+        """Test project_id is nullable for global facts."""
+        columns = Fact.__table__.columns
+        assert columns["project_id"].nullable
+
+
+class TestProcedureModel:
+    """Tests for Procedure model."""
+
+    def test_tablename(self) -> None:
+        """Test table name is correct."""
+        assert Procedure.__tablename__ == "procedures"
+
+    def test_has_required_columns(self) -> None:
+        """Test all required columns exist."""
+        columns = Procedure.__table__.columns
+        required = [
+            "id",
+            "project_id",
+            "agent_type_id",
+            "name",
+            "trigger_pattern",
+            "steps",
+            "success_count",
+            "failure_count",
+            "last_used",
+            "embedding",
+            "created_at",
+            "updated_at",
+        ]
+        for col in required:
+            assert col in columns, f"Missing column: {col}"
+
+    def test_success_rate_property(self) -> None:
+        """Test success_rate calculated property."""
+        proc = Procedure()
+        proc.success_count = 8
+        proc.failure_count = 2
+        assert proc.success_rate == 0.8
+
+    def test_success_rate_zero_total(self) -> None:
+        """Test success_rate with zero total uses."""
+        proc = Procedure()
+        proc.success_count = 0
+        proc.failure_count = 0
+        assert proc.success_rate == 0.0
+
+    def test_total_uses_property(self) -> None:
+        """Test total_uses calculated property."""
+        proc = Procedure()
+        proc.success_count = 5
+        proc.failure_count = 3
+        assert proc.total_uses == 8
+
+
+class TestMemoryConsolidationLogModel:
+    """Tests for MemoryConsolidationLog model."""
+
+    def test_tablename(self) -> None:
+        """Test table name is correct."""
+        assert MemoryConsolidationLog.__tablename__ == "memory_consolidation_log"
+
+    def test_has_required_columns(self) -> None:
+        """Test all required columns exist."""
+        columns = MemoryConsolidationLog.__table__.columns
+        required = [
+            "id",
+            "consolidation_type",
+            "source_count",
+            "result_count",
+            "started_at",
+            "completed_at",
+            "status",
+            "error",
+            "created_at",
+            "updated_at",
+        ]
+        for col in required:
+            assert col in columns, f"Missing column: {col}"
+
+    def test_duration_seconds_property_completed(self) -> None:
+        """Test duration_seconds with completed job."""
+        log = MemoryConsolidationLog()
+        log.started_at = datetime.now(UTC)
+        log.completed_at = log.started_at + timedelta(seconds=10)
+        assert log.duration_seconds == pytest.approx(10.0)
+
+    def test_duration_seconds_property_incomplete(self) -> None:
+        """Test duration_seconds with incomplete job."""
+        log = MemoryConsolidationLog()
+        log.started_at = datetime.now(UTC)
+        log.completed_at = None
+        assert log.duration_seconds is None
+
+    def test_default_status(self) -> None:
+        """Test default status is PENDING."""
+        columns = MemoryConsolidationLog.__table__.columns
+        assert columns["status"].default.arg == ConsolidationStatus.PENDING
+
+
+class TestModelExports:
+    """Tests for model package exports."""
+
+    def test_all_models_exported(self) -> None:
+        """Test all models are exported from package."""
+        from app.models.memory import (
+            Episode,
+            Fact,
+            MemoryConsolidationLog,
+            Procedure,
+            WorkingMemory,
+        )
+
+        # Verify these are the actual classes
+        assert Episode.__tablename__ == "episodes"
+        assert Fact.__tablename__ == "facts"
+        assert Procedure.__tablename__ == "procedures"
+        assert WorkingMemory.__tablename__ == "working_memory"
+        assert MemoryConsolidationLog.__tablename__ == "memory_consolidation_log"
+
+    def test_enums_exported(self) -> None:
+        """Test all enums are exported."""
+        assert ScopeType.GLOBAL.value == "global"
+        assert EpisodeOutcome.SUCCESS.value == "success"
+        assert ConsolidationType.WORKING_TO_EPISODIC.value == "working_to_episodic"
+        assert ConsolidationStatus.PENDING.value == "pending"