```

refactor(api): 使用常量替代硬编码字符串

- 在health_check接口中使用ApiResponseKey.STATUS和ApiStatus.OK常量
- 替换硬编码的状态返回值为枚举常量

refactor(core): 配置模块错误信息统一使用常量

- 从constants模块导入ConfigErrorDetail并替换CORS_ORIGINS和LEGACY_ALLOWED_QUERIES的验证错误信息
- 配置类中的默认值使用constants中定义的常量

feat(constants): 添加API响应、安全错误和配置错误常量类

- 新增ApiResponseKey用于API状态键名
- 新增ApiStatus用于API状态值
- 新增SecurityErrorDetail用于安全认证错误详情
- 新增ConfigErrorDetail用于配置验证错误详情
- 添加DEFAULT_MODEL_PROVIDER和DEFAULT_OPENCLAW_ACTION_JSON常量

refactor(security): 安全认证模块使用错误常量

- 将硬编码的安全错误信息替换为SecurityErrorDetail常量
- 包括API密钥、审批密钥和审计密钥的相关错误信息

refactor(ai-agent): AI代理适配器改进错误处理

- 将HTTP状态码替换为FastAPI状态常量
- 添加OpenClaw工具和操作的错误常量
- 修复健康检查和工具调用中的状态码比较逻辑
- 添加AIToolAuditKey用于工具审计键名

feat(ai-agent): 扩展AI代理常量定义

- 新增AIToolAuditKey用于工具审计字段
- 添加OpenClaw相关的错误常量如OPENCLAW_CHAT_PROVIDER_REQUIRED等
- 添加UNSUPPORTED_AI_SKILL_TEMPLATE模板字符串

refactor(approvals): 审批模块常量化重构

- 新增ApprovalPayloadKey用于审批载荷字段
- 添加approval_action函数和APPROVAL_ACTION_SEPARATOR分隔符
- 使用常量替换字面量值

feat(audit): 审计模块新增飞书事件动作类型

- 添加FEISHU_WEBHOOK_EVENT和FEISHU_LONG_CONNECTION_EVENT审计动作

refactor(business): 业务模块全面常量化

- 新增BusinessDomain枚举包含所有业务域
- 添加BusinessResponseKey、BusinessPayloadKey等常量类
- 重构DOMAIN_MODELS为frozenset以提高性能
- 添加normalize_domain等辅助函数用于域标准化
- 使用常量替换路由和业务服务中的硬编码字符串
- 添加业务错误常量和字段验证模板

refactor(feishu): 飞书客户端错误处理优化

- 将HTTP状态码替换为FastAPI标准状态常量
- 改进错误处理的一致性

refactor(approvals): 审批服务使用新常量结构

- 使用ApprovalPayloadKey常量重构载荷字段
- 使用approval_action函数统一动作命名格式
- 优化高风险域判断逻辑
```

app/modules/legacy_mysql/constants.py

@@ -5,6 +5,71 @@ class LegacyQueryName(StrEnum):
     PROJECTS = "projects"
 
 
+class LegacyResponseKey(StrEnum):
+    STATUS = "status"
+    COLUMNS = "columns"
+    ROWS = "rows"
+    ROW_COUNT = "row_count"
+    DRY_RUN = "dry_run"
+    CREATED = "created"
+    UPDATED = "updated"
+    SKIPPED = "skipped"
+    ITEMS = "items"
+    ACTION = "action"
+    REASON = "reason"
+    SOURCE = "source"
+    PROJECT = "project"
+    SYNC_RUN_CODE = "sync_run_code"
+    SOURCE_QUERY = "source_query"
+    FIELD_MAP = "field_map"
+    LIMIT = "limit"
+
+
+class LegacyProjectField(StrEnum):
+    ID = "id"
+    CODE = "code"
+    EXTERNAL_ID = "external_id"
+    SOURCE_SYSTEM = "source_system"
+    NAME = "name"
+    OWNER = "owner"
+    STATUS = "status"
+    PROGRESS = "progress"
+    PROGRESS_PERCENT = "progress_percent"
+    START_DATE = "start_date"
+    DUE_DATE = "due_date"
+    BUDGET = "budget"
+    BUDGET_AMOUNT = "budget_amount"
+    ACTUAL_COST = "actual_cost"
+    ACTUAL_AMOUNT = "actual_amount"
+    DESCRIPTION = "description"
+
+
+class LegacySyncAction(StrEnum):
+    CREATE = "create"
+    UPDATE = "update"
+    SKIPPED = "skipped"
+    ALLOWLISTED_INLINE_SQL = "allowlisted_inline_sql"
+
+
 class LegacyQueryError(StrEnum):
+    DATABASE_NOT_CONFIGURED = "LEGACY_DATABASE_URL is not configured"
     QUERY_NOT_ALLOWED = "Legacy query is not in the configured allowlist"
     PROJECT_QUERY_NOT_CONFIGURED = "LEGACY_PROJECT_QUERY is not configured. Configure it first."
+    ONLY_SELECT_ALLOWED = "Only SELECT statements are allowed"
+    FORBIDDEN_SQL_TOKEN = "Forbidden SQL token in readonly query"
+    INVALID_LIMIT = "Invalid readonly query limit"
+    APP_DB_UNAVAILABLE = "Application database session is not available"
+
+
+LEGACY_SYNC_RUN_CODE_PREFIX = "SYNC-PROJECTS"
+LEGACY_PROJECT_QUERY_SOURCE = "LEGACY_PROJECT_QUERY"
+LEGACY_SYNC_MISSING_ID_REASON = "missing external_id/code"
+LEGACY_PROJECT_SYNC_NOTE = "Project sync from readonly legacy MySQL"
+LEGACY_MYSQL_CONNECTION_FAILED_TEMPLATE = "MySQL connection failed: {error}"
+LEGACY_HEALTH_SQL = "SELECT 1"
+LEGACY_SELECT_PREFIX = "select"
+LEGACY_SQL_TRAILING_TERMINATOR = ";"
+LEGACY_LIMIT_MARKER = " limit "
+LEGACY_LIMIT_CLAUSE = " LIMIT :limit"
+LEGACY_PROJECT_CODE_TEMPLATE = "{prefix}-{external_id}"
+LEGACY_UNNAMED_PROJECT = "未命名项目"