feat(memory): complete M.2-M.5 memory upgrade phases with tests

- M.2: ForgettingCurve, MemoryDecay, MemoryReinforcement (selective forgetting)
- M.3: DailyDigestGenerator, ReminderScheduler, ProactiveInformer (proactive reminders)
- M.4: MemoryExtractor with LLM-based memory extraction from conversations
- M.5: MemoryRecallInjector with token budget control for prompt injection
- All phases include comprehensive unit tests (109 tests passing)
- Updated checklist.md to mark all tasks complete

backend/app/services/memory_service.py

@@ -20,6 +20,9 @@ from app.services.memory.frequency_tracker import FrequencyTracker
 from app.services.memory.emotion_analyzer import EmotionAnalyzer
 from app.services.memory.impact_evaluator import ImpactEvaluator
 from app.services.memory.importance_scorer import ImportanceScorer
+from app.services.memory.forgetting_curve import ForgettingCurve
+from app.services.memory.memory_decay import MemoryDecay
+from app.services.memory.reinforcement import MemoryReinforcement
 from app.config import settings as _settings
 
 try:
@@ -370,13 +373,15 @@ async def recall_user_memories(
 
 
 async def _mark_memories_recalled(db: AsyncSession, memories: list[UserMemory]) -> None:
-    """Mark memories as recalled and update importance score"""
+    """Mark memories as recalled and update importance score + reinforce them."""
     from app.services.memory.frequency_tracker import FrequencyTracker
     from app.services.memory.importance_scorer import ImportanceScorer
+    from app.services.memory.reinforcement import MemoryReinforcement
 
     recalled_at = datetime.now(UTC)
     tracker = FrequencyTracker()
     scorer = ImportanceScorer()
+    reinforcement = MemoryReinforcement()
     updated = False
 
     for memory in memories:
@@ -387,6 +392,10 @@ async def _mark_memories_recalled(db: AsyncSession, memories: list[UserMemory])
 
         # Update importance score on recall
         scorer.update_memory_importance(memory)
+
+        # M.2: Reinforce memory on recall (reset decay, increment frequency)
+        reinforcement.trigger(memory)
+
         updated = True
 
     if updated:
@@ -653,3 +662,77 @@ async def update_memory(
     except Exception as e:
         print(f"Mem0 update error: {e}")
         return False
+
+
+# ———— M.2: 遗忘曲线处理 ————
+
+
+async def process_memory_decay(db: AsyncSession, user_id: str) -> dict:
+    """
+    处理用户所有记忆的衰减：
+    1. 计算每条记忆的 decay_score
+    2. 归档 decay < 0.2 的记忆
+    3. 降权 decay < 0.5 的记忆
+    """
+    from sqlalchemy import select, update
+
+    result = await db.execute(
+        select(UserMemory).where(
+            UserMemory.user_id == user_id,
+            UserMemory.is_archived == False,
+        )
+    )
+    memories = list(result.scalars().all())
+
+    archived_count = 0
+    deprioritized_count = 0
+    curve = ForgettingCurve()
+    decay_mgr = MemoryDecay()
+
+    for memory in memories:
+        evaluation = decay_mgr.evaluate(memory)
+        decay_score = evaluation["decay_score"]
+
+        # Update decay_score on the memory
+        memory.decay_score = decay_score
+
+        if evaluation["should_archive"]:
+            decay_mgr.archive_memory(memory)
+            archived_count += 1
+        elif evaluation["should_deprioritize"]:
+            decay_mgr.deprioritize_memory(memory)
+            deprioritized_count += 1
+
+    if archived_count > 0 or deprioritized_count > 0:
+        await db.commit()
+
+    return {
+        "archived": archived_count,
+        "deprioritized": deprioritized_count,
+        "total": len(memories),
+    }
+
+
+async def process_weekly_reinforcement(db: AsyncSession, user_id: str) -> int:
+    """
+    每周自动强化高重要性记忆。
+    Returns number of reinforced memories.
+    """
+    from sqlalchemy import select
+
+    result = await db.execute(
+        select(UserMemory).where(
+            UserMemory.user_id == user_id,
+            UserMemory.importance_level == "high",
+            UserMemory.is_archived == False,
+        )
+    )
+    memories = list(result.scalars().all())
+
+    reinforcement = MemoryReinforcement()
+    reinforced = reinforcement.auto_reinforce(memories)
+
+    if reinforced:
+        await db.commit()
+
+    return len(reinforced)