feat(learning): 實作 Playbook 信心度調整機制 (ADR-030)

- 新增 _promote_playbook: 高評分提升信心度 +0.1
- 新增 _demote_playbook: 低評分降低信心度 -0.15
- 新增 find_by_source_incident: 按 incident_id 查詢 Playbook
- 新增 adjust_confidence: 信心度調整 + 狀態自動轉換
- 新增 Playbook.failure_rate 屬性

自動狀態轉換:
- ai_confidence >= 0.9 + DRAFT → 自動 APPROVED
- ai_confidence < 0.3 + failure_rate > 50% → 自動 DEPRECATED

測試: 13 案例全部通過

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

apps/api/src/services/learning_service.py

@@ -432,16 +432,112 @@ class LearningService:
             return None
 
     async def _promote_playbook(self, incident_id: str) -> bool:
-        """提升 Playbook 信心度 (高評分)"""
-        # TODO: 實作 Playbook 信心度提升邏輯
-        logger.debug("playbook_promoted", incident_id=incident_id)
-        return True
+        """
+        提升 Playbook 信心度 (高評分)
+
+        2026-03-30 Claude Code: 實作信心度提升邏輯
+
+        邏輯:
+        - 尋找 source_incident_ids 包含此 incident_id 的 Playbooks
+        - 提升 ai_confidence +0.1 (上限 1.0)
+        - 若信心度 >= 0.9 且 status == DRAFT → 自動升級為 APPROVED
+        """
+        try:
+            from src.repositories.playbook_repository import get_playbook_repository
+
+            repo = get_playbook_repository()
+            playbooks = await repo.find_by_source_incident(incident_id)
+
+            if not playbooks:
+                logger.debug(
+                    "playbook_promote_no_match",
+                    incident_id=incident_id,
+                )
+                return False
+
+            # 信心度提升參數
+            CONFIDENCE_BOOST = 0.1
+
+            updated_count = 0
+            for playbook in playbooks:
+                result = await repo.adjust_confidence(
+                    playbook_id=playbook.playbook_id,
+                    delta=CONFIDENCE_BOOST,
+                    reason=f"High effectiveness rating from incident {incident_id}",
+                )
+                if result:
+                    updated_count += 1
+
+            logger.info(
+                "playbook_promoted",
+                incident_id=incident_id,
+                updated_count=updated_count,
+                total_playbooks=len(playbooks),
+            )
+
+            return updated_count > 0
+
+        except Exception as e:
+            logger.warning(
+                "playbook_promote_failed",
+                incident_id=incident_id,
+                error=str(e),
+            )
+            return False
 
     async def _demote_playbook(self, incident_id: str) -> bool:
-        """降低 Playbook 信心度 (低評分)"""
-        # TODO: 實作 Playbook 信心度降低邏輯
-        logger.debug("playbook_demoted", incident_id=incident_id)
-        return True
+        """
+        降低 Playbook 信心度 (低評分)
+
+        2026-03-30 Claude Code: 實作信心度降低邏輯
+
+        邏輯:
+        - 尋找 source_incident_ids 包含此 incident_id 的 Playbooks
+        - 降低 ai_confidence -0.15 (下限 0.0)
+        - 若信心度 < 0.3 且 failure_rate > 50% → 自動降級為 DEPRECATED
+        """
+        try:
+            from src.repositories.playbook_repository import get_playbook_repository
+
+            repo = get_playbook_repository()
+            playbooks = await repo.find_by_source_incident(incident_id)
+
+            if not playbooks:
+                logger.debug(
+                    "playbook_demote_no_match",
+                    incident_id=incident_id,
+                )
+                return False
+
+            # 信心度降低參數 (懲罰比獎勵更重，避免低品質 Playbook 累積)
+            CONFIDENCE_PENALTY = -0.15
+
+            updated_count = 0
+            for playbook in playbooks:
+                result = await repo.adjust_confidence(
+                    playbook_id=playbook.playbook_id,
+                    delta=CONFIDENCE_PENALTY,
+                    reason=f"Low effectiveness rating from incident {incident_id}",
+                )
+                if result:
+                    updated_count += 1
+
+            logger.info(
+                "playbook_demoted",
+                incident_id=incident_id,
+                updated_count=updated_count,
+                total_playbooks=len(playbooks),
+            )
+
+            return updated_count > 0
+
+        except Exception as e:
+            logger.warning(
+                "playbook_demote_failed",
+                incident_id=incident_id,
+                error=str(e),
+            )
+            return False
 
     # =========================================================================
     # 🆕 Phase D-G P0 修正: 新增方法