Add log system with three log types (agent/system/chat)

Implemented a complete log system for tracking:
- Agent logs:智能体调用
- System logs: 系统运行
- Chat logs: 问答对话

Backend:
- Log model with type, level, user_id, message, source, duration_ms
- LogService with methods for logging and querying
- API endpoints: GET /api/logs, GET /api/logs/stats, GET /api/logs/recent

Frontend:
- LogView.vue with filters, stats, pagination, auto-refresh
- log.ts API client with TypeScript interfaces
- Added "运行日志" nav item to sidebar

backend/app/routers/log.py

@@ -0,0 +1,93 @@
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.ext.asyncio import AsyncSession
+from pydantic import BaseModel
+from typing import Optional
+from app.database import get_db
+from app.models.user import User
+from app.routers.auth import get_current_user
+from app.services.log_service import LogService
+
+router = APIRouter(prefix="/api/logs", tags=["Log"])
+
+
+class LogOut(BaseModel):
+    id: str
+    level: str
+    type: str
+    user_id: Optional[str]
+    message: str
+    source: Optional[str]
+    details: Optional[str]
+    duration_ms: Optional[str]
+    created_at: str
+    updated_at: str
+
+    model_config = {"from_attributes": True}
+
+
+class LogStatsOut(BaseModel):
+    total: int
+    by_type: dict
+    by_level: dict
+
+
+class LogQueryOut(BaseModel):
+    logs: list[LogOut]
+    total: int
+    page: int
+    page_size: int
+
+
+@router.get("", response_model=LogQueryOut)
+async def list_logs(
+    log_type: Optional[str] = Query(None, description="日志类型: agent/system/chat"),
+    level: Optional[str] = Query(None, description="日志级别: debug/info/warning/error"),
+    source: Optional[str] = Query(None, description="来源模块"),
+    page: int = Query(1, ge=1),
+    page_size: int = Query(50, ge=1, le=200),
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """查询日志列表"""
+    svc = LogService(db)
+    offset = (page - 1) * page_size
+    logs, total = await svc.list_logs(
+        log_type=log_type,
+        level=level,
+        user_id=current_user.id,
+        source=source,
+        limit=page_size,
+        offset=offset,
+    )
+    return LogQueryOut(
+        logs=[LogOut.model_validate(log) for log in logs],
+        total=total,
+        page=page,
+        page_size=page_size,
+    )
+
+
+@router.get("/stats", response_model=LogStatsOut)
+async def get_log_stats(
+    hours: int = Query(24, ge=1, le=168),
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """获取日志统计"""
+    svc = LogService(db)
+    stats = await svc.get_log_stats(hours=hours)
+    return LogStatsOut(**stats)
+
+
+@router.get("/recent", response_model=list[LogOut])
+async def get_recent_logs(
+    log_type: Optional[str] = Query(None),
+    hours: int = Query(24, ge=1, le=168),
+    limit: int = Query(50, ge=1, le=200),
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """获取最近的日志"""
+    svc = LogService(db)
+    logs = await svc.get_recent_logs(log_type=log_type, hours=hours, limit=limit)
+    return [LogOut.model_validate(log) for log in logs]