fix: 補建 AIInsight ORM 模型（ai_insights 表缺少 class 定義）

ai_insights 表在 DB 存在且有 39 筆資料，但 database/ai_models.py 從未定義
AIInsight class，導致 quality_rescore_task、openclaw_learning_service
以及所有 AI KM 讀寫全部 ImportError 崩潰。
同步補入 __all__ 匯出，修復 embedding_retry_queue 2 筆卡住。

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

database/ai_models.py

@@ -119,7 +119,50 @@ class AIUsageTracking(Base):
             'created_at': self.created_at.isoformat() if self.created_at else None
         }
 
+class AIInsight(Base):
+    """
+    AI 洞察知識庫（ai_insights 表）— KM 沉澱核心，支援 RAG 向量化。
+    對應 openclaw_learning_service / scheduler 各任務寫入。
+    """
+    __tablename__ = 'ai_insights'
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    insight_type = Column(String(50), nullable=False)   # backup_status / human_review / auto_heal_playbook 等
+    period = Column(String(50))                          # 分析週期，e.g. "2026-04-20"
+    product_sku = Column(String(50))
+    content = Column(Text, nullable=False)
+    metadata_json = Column(Text)                         # JSON extra payload
+    avg_quality = Column(Float, default=0.0)
+    status = Column(String(20), default='active')        # active / archived
+    decay_exempt = Column(Boolean, default=False)
+    ai_model = Column(String(50))
+    feedback_up = Column(Integer, default=0)
+    feedback_down = Column(Integer, default=0)
+    confidence = Column(Float, default=1.0)
+    created_by = Column(String(50))
+    created_at = Column(DateTime, default=datetime.now)
+    updated_at = Column(DateTime, default=datetime.now, onupdate=datetime.now)
+    # embedding 欄位為 pgvector 型別，透過 raw SQL 寫入，此處不聲明以避免型別衝突
+
+    def to_dict(self):
+        return {
+            'id': self.id,
+            'insight_type': self.insight_type,
+            'period': self.period,
+            'product_sku': self.product_sku,
+            'content': self.content,
+            'avg_quality': self.avg_quality,
+            'status': self.status,
+            'ai_model': self.ai_model,
+            'feedback_up': self.feedback_up,
+            'feedback_down': self.feedback_down,
+            'confidence': self.confidence,
+            'created_by': self.created_by,
+            'created_at': self.created_at.isoformat() if self.created_at else None,
+        }
+
+
 __all__ = [
     "AgentContext", "ActionPlan", "ActionOutcome", "AgentStrategyWeights",
-    "AIGenerationHistory", "AIPromptTemplate", "AIUsageTracking"
+    "AIGenerationHistory", "AIPromptTemplate", "AIUsageTracking", "AIInsight",
 ]