feat(memory): implement memory consolidation service and tasks (#95)

- Add MemoryConsolidationService with Working→Episodic→Semantic/Procedural transfer
- Add Celery tasks for session and nightly consolidation
- Implement memory pruning with importance-based retention
- Add comprehensive test suite (32 tests)

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

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

backend/app/services/memory/consolidation/__init__.py

@@ -1,10 +1,29 @@
+# app/services/memory/consolidation/__init__.py
 """
-Memory Consolidation
+Memory Consolidation.
 
 Transfers and extracts knowledge between memory tiers:
-- Working -> Episodic
-- Episodic -> Semantic
-- Episodic -> Procedural
+- Working -> Episodic (session end)
+- Episodic -> Semantic (learn facts)
+- Episodic -> Procedural (learn procedures)
+
+Also handles memory pruning and importance-based retention.
 """
 
-# Will be populated in #95
+from .service import (
+    ConsolidationConfig,
+    ConsolidationResult,
+    MemoryConsolidationService,
+    NightlyConsolidationResult,
+    SessionConsolidationResult,
+    get_consolidation_service,
+)
+
+__all__ = [
+    "ConsolidationConfig",
+    "ConsolidationResult",
+    "MemoryConsolidationService",
+    "NightlyConsolidationResult",
+    "SessionConsolidationResult",
+    "get_consolidation_service",
+]