feat: 审核规则模版+设置页面整合+去掉角色切换demo

后端:
- AuditRule 新增 value 字段, rule_type 扩展 DDL/DML
- MySQL/PG/Redis 预设规则种子接口 POST /audit-rules/seed/{db_type}
- 公告管理 CRUD (announcements)
- 消息推送 CRUD+测试 (notifications: 钉钉/飞书/邮件)
- LDAP 配置 CRUD+测试连接 (ldap-config)
- 164 tests passing (+31 新增)

前端:
- AuditRulesPage 重写: DB类型Tab+DDL/DML分组+参数编辑
- SettingsPage: 系统设置主页(审核规则/公告/推送/LDAP)
- NotificationPage: 钉钉/飞书/SMTP配置
- LdapConfigPage: LDAP设置+测试连接
- AnnouncementPage: 公告Markdown编辑
- 去掉左下角角色切换demo
- 侧边栏合并为: 系统设置(含审核规则+公告+推送+LDAP)

backend/app/api/v1/endpoints/announcement.py

@@ -0,0 +1,93 @@
+from datetime import datetime, timezone
+from typing import List
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.database import get_db
+from app.core.security import get_current_user, require_role
+from app.models.user import User
+from app.models.announcement import Announcement
+from app.schemas.announcement import (
+    AnnouncementCreate,
+    AnnouncementUpdate,
+    AnnouncementResponse,
+)
+
+router = APIRouter(prefix="/announcements", tags=["公告管理"])
+
+
+@router.get("", response_model=List[AnnouncementResponse])
+async def list_announcements(
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """所有登录用户可查看公告列表"""
+    stmt = select(Announcement).order_by(Announcement.id.desc())
+    result = await db.execute(stmt)
+    return result.scalars().all()
+
+
+@router.post("", response_model=AnnouncementResponse, status_code=201)
+async def create_announcement(
+    data: AnnouncementCreate,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(require_role("admin")),
+):
+    """管理员创建公告"""
+    announcement = Announcement(
+        title=data.title,
+        content=data.content,
+        is_published=False,
+    )
+    db.add(announcement)
+    await db.commit()
+    await db.refresh(announcement)
+    return announcement
+
+
+@router.put("/{announcement_id}", response_model=AnnouncementResponse)
+async def update_announcement(
+    announcement_id: int,
+    data: AnnouncementUpdate,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(require_role("admin")),
+):
+    """管理员更新公告"""
+    result = await db.execute(
+        select(Announcement).where(Announcement.id == announcement_id)
+    )
+    announcement = result.scalar_one_or_none()
+    if not announcement:
+        raise HTTPException(status_code=404, detail="公告不存在")
+
+    update_data = data.model_dump(exclude_unset=True)
+    # If publishing for the first time, set published_at
+    if update_data.get("is_published") and not announcement.published_at:
+        announcement.published_at = datetime.now(timezone.utc)
+
+    for key, value in update_data.items():
+        setattr(announcement, key, value)
+    await db.commit()
+    await db.refresh(announcement)
+    return announcement
+
+
+@router.delete("/{announcement_id}")
+async def delete_announcement(
+    announcement_id: int,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(require_role("admin")),
+):
+    """管理员删除公告"""
+    result = await db.execute(
+        select(Announcement).where(Announcement.id == announcement_id)
+    )
+    announcement = result.scalar_one_or_none()
+    if not announcement:
+        raise HTTPException(status_code=404, detail="公告不存在")
+
+    await db.delete(announcement)
+    await db.commit()
+    return {"message": "公告已删除"}