Add brain memory services and APIs

Introduce the backend pieces for brain memory ingestion, routing, and
system telemetry so the new knowledge workflows can project data into a
brain view. The supporting tests lock in the new behavior and keep the
expanded backend surface stable.

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

backend/app/models/log.py

@@ -1,4 +1,4 @@
-from sqlalchemy import Column, String, Text, DateTime, Index, Enum as SQLEnum
+from sqlalchemy import Column, String, Text, Integer, Index
 from app.models.base import BaseModel
 import enum
 
@@ -22,12 +22,20 @@ class Log(BaseModel):
     level = Column(String(20), default=LogLevel.INFO.value, index=True)  # debug/info/warning/error
     type = Column(String(20), default=LogType.SYSTEM.value, index=True)   # agent/system/chat
     user_id = Column(String(36), nullable=True, index=True)  # 关联用户
+    request_id = Column(String(64), nullable=True, index=True)
+    route = Column(String(255), nullable=True, index=True)
+    method = Column(String(16), nullable=True, index=True)
+    status_code = Column(Integer, nullable=True, index=True)
+    error_type = Column(String(100), nullable=True)
+    operation = Column(String(100), nullable=True, index=True)
     message = Column(Text, nullable=False)  # 日志内容
     details = Column(Text, nullable=True)  # 详细信息(JSON)
     source = Column(String(100), nullable=True)  # 来源模块
-    duration_ms = Column(String(20), nullable=True)  # 执行耗时
+    duration_ms = Column(Integer, nullable=True)  # 执行耗时
 
     __table_args__ = (
         Index('idx_logs_type_level', 'type', 'level'),
         Index('idx_logs_created_at', 'created_at'),
+        Index('idx_logs_request_id', 'request_id'),
+        Index('idx_logs_operation_status', 'operation', 'status_code'),
     )