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/schemas/audit_rule.py

@@ -6,10 +6,11 @@ from typing import Optional, Literal
 class AuditRuleCreate(BaseModel):
     name: str = Field(..., min_length=1, max_length=100)
     description: Optional[str] = None
-    rule_type: Literal["syntax", "performance", "safety", "naming"]
+    rule_type: Literal["syntax", "performance", "safety", "naming", "DDL", "DML"]
     severity: Literal["error", "warning", "info"] = "warning"
     db_type: str = "mysql"
     pattern: Optional[str] = None
+    value: Optional[str] = Field(default=None, max_length=255)
     is_enabled: bool = True
     message: str = Field(..., min_length=1, max_length=500)
 
@@ -17,10 +18,11 @@ class AuditRuleCreate(BaseModel):
 class AuditRuleUpdate(BaseModel):
     name: Optional[str] = Field(default=None, min_length=1, max_length=100)
     description: Optional[str] = None
-    rule_type: Optional[Literal["syntax", "performance", "safety", "naming"]] = None
+    rule_type: Optional[Literal["syntax", "performance", "safety", "naming", "DDL", "DML"]] = None
     severity: Optional[Literal["error", "warning", "info"]] = None
     db_type: Optional[str] = None
     pattern: Optional[str] = None
+    value: Optional[str] = Field(default=None, max_length=255)
     is_enabled: Optional[bool] = None
     message: Optional[str] = Field(default=None, min_length=1, max_length=500)
 
@@ -33,6 +35,7 @@ class AuditRuleResponse(BaseModel):
     severity: str
     db_type: str
     pattern: Optional[str] = None
+    value: Optional[str] = None
     is_enabled: bool
     message: str
     created_at: datetime