feat(memory): add memory consolidation task and switch source_episode_ids to JSON

- Added `memory_consolidation` to the task list and updated `__all__` in test files.
- Updated `source_episode_ids` in `Fact` model to use JSON for cross-database compatibility.
- Revised related database migrations to use JSONB instead of ARRAY.
- Adjusted test concurrency in Makefile for improved test performance.

backend/app/models/memory/fact.py

@@ -18,11 +18,9 @@ from sqlalchemy import (
     Text,
     text,
 )
-from sqlalchemy.dialects.postgresql import (
-    ARRAY,
-    UUID as PGUUID,
-)
+from sqlalchemy.dialects.postgresql import UUID as PGUUID
 from sqlalchemy.orm import relationship
+from sqlalchemy.types import JSON
 
 from app.models.base import Base, TimestampMixin, UUIDMixin
 
@@ -63,10 +61,8 @@ class Fact(Base, UUIDMixin, TimestampMixin):
     # Confidence score (0.0 to 1.0)
     confidence = Column(Float, nullable=False, default=0.8, index=True)
 
-    # Source tracking: which episodes contributed to this fact
-    source_episode_ids: Column[list] = Column(
-        ARRAY(PGUUID(as_uuid=True)), default=list, nullable=False
-    )
+    # Source tracking: which episodes contributed to this fact (stored as JSON array of UUID strings)
+    source_episode_ids: Column[list] = Column(JSON, default=list, nullable=False)
 
     # Learning history
     first_learned = Column(DateTime(timezone=True), nullable=False)
@@ -94,8 +90,7 @@ class Fact(Base, UUIDMixin, TimestampMixin):
         Index("ix_facts_subject_predicate", "subject", "predicate"),
         Index("ix_facts_project_subject", "project_id", "subject"),
         Index("ix_facts_confidence_time", "confidence", "last_reinforced"),
-        # For finding facts by entity (subject or object)
-        Index("ix_facts_subject", "subject"),
+        # Note: subject already has index=True on Column definition, no need for explicit index
         # Data integrity constraints
         CheckConstraint(
             "confidence >= 0.0 AND confidence <= 1.0",