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/instance.py

@@ -10,6 +10,8 @@ from app.models.user import User
 from app.models.instance import Instance
 from app.schemas.instance import InstanceCreate, InstanceUpdate, InstanceResponse, ConnectionTestResult
 from app.services.instance_service import InstanceService
+from app.core.crypto import encrypt_password, decrypt_password
+from app.services.audit_log_service import AuditLogService
 
 router = APIRouter(prefix="/instances", tags=["数据源管理"])
 
@@ -42,12 +44,18 @@ async def create_instance(
         host=data.host,
         port=data.port,
         username=data.username,
-        password=data.password,
+        password=encrypt_password(data.password),
         database=data.database,
         env=data.env,
         description=data.description,
     )
     db.add(instance)
+    await db.flush()
+    await AuditLogService.log(
+        db, user_id=current_user.id, action="CREATE_INSTANCE",
+        target_type="instance", target_id=instance.id,
+        detail=f"创建数据源: {data.name} ({data.db_type}@{data.host}:{data.port})",
+    )
     await db.commit()
     await db.refresh(instance)
     return instance
@@ -79,6 +87,8 @@ async def update_instance(
         raise HTTPException(status_code=404, detail="数据源不存在")
 
     update_data = data.model_dump(exclude_unset=True)
+    if "password" in update_data:
+        update_data["password"] = encrypt_password(update_data["password"])
     for key, value in update_data.items():
         setattr(instance, key, value)
     await db.commit()
@@ -97,6 +107,11 @@ async def delete_instance(
     if not instance:
         raise HTTPException(status_code=404, detail="数据源不存在")
 
+    await AuditLogService.log(
+        db, user_id=current_user.id, action="DELETE_INSTANCE",
+        target_type="instance", target_id=instance.id,
+        detail=f"删除数据源: {instance.name}",
+    )
     await db.delete(instance)
     await db.commit()
     return {"message": "数据源已删除"}
@@ -113,7 +128,18 @@ async def test_connection(
     if not instance:
         raise HTTPException(status_code=404, detail="数据源不存在")
 
-    return await InstanceService.test_connection(instance)
+    # Decrypt password for connection test
+    from app.models.instance import Instance as InstModel
+    decrypted = instance.__class__(
+        name=instance.name, db_type=instance.db_type, host=instance.host,
+        port=instance.port, username=instance.username,
+        password=decrypt_password(instance.password),
+        database=instance.database, env=instance.env,
+        description=instance.description, status=instance.status,
+        version=instance.version,
+    )
+    decrypted.id = instance.id
+    return await InstanceService.test_connection(decrypted)
 
 
 @router.get("/{instance_id}/databases")