feat: Phase 3 - AES encryption, SQL audit engine, audit logs (85 tests)

Phase 3.1: Instance password AES-256-GCM encryption
Phase 3.2: SQL audit rule engine (10 rules)
Phase 3.3: Auto-audit on ticket creation
Phase 3.4: Operation audit logs + GET /audit/logs
Tests: 44 -> 85 (41 new), Frontend: AuditLogsPage

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

@@ -0,0 +1,27 @@
+"""Audit log endpoints."""
+from typing import Optional
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.database import get_db
+from app.core.security import require_role
+from app.models.user import User
+from app.services.audit_log_service import AuditLogService
+
+router = APIRouter(prefix="/audit", tags=["审计日志"])
+
+
+@router.get("/logs")
+async def list_audit_logs(
+    page: int = Query(1, ge=1),
+    page_size: int = Query(20, ge=1, le=100),
+    user_id: Optional[int] = None,
+    action: Optional[str] = None,
+    target_type: Optional[str] = None,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(require_role("admin", "dba")),
+):
+    return await AuditLogService.list_logs(
+        db, page=page, page_size=page_size,
+        user_id=user_id, action=action, target_type=target_type,
+    )