fix: code compliance audit and fix across all services

NestJS (6 services): implement @RequirePermission decorator with
SetMetadata+Reflector, register APP_GUARD globally, fix as assertions
to type guards, add explicit return types, fix import type for express,
fix /metrics implicit any, replace native Error with ApplicationError,
remove typeorm remnants, register LifecycleService.

teacher-bff: add logger, ApplicationError, GlobalErrorFilter, forward
real userId to downstream, log downstream failures, migrate health
controller to shared/health.

Go (2 services): interface to any, doc comments, CORS dev whitelist,
JWT secret fail-fast, push-gateway internal API auth, metrics and
readyz endpoints, remove dead code.

Python (2 services): lifespan return type, dev_mode to bool, data-ana
APIRouter, ai POST body model, ClickHouse async wrapping.

services/ai/src/ai/config.py

@@ -12,7 +12,7 @@ class Settings(BaseSettings):
     openai_base_url: str = "https://api.openai.com/v1"
     anthropic_api_key: str = ""
     # 开发模式：true 时跳过 OTel exporter 初始化，避免本地无 collector 时报错
-    dev_mode: str = "false"
+    dev_mode: bool = False
     # 可观测性
     otel_endpoint: str = "http://localhost:4318"
     log_level: str = "info"
@@ -22,7 +22,7 @@ class Settings(BaseSettings):
     @property
     def is_dev(self) -> bool:
         """是否处于开发模式."""
-        return self.dev_mode.lower() == "true"
+        return self.dev_mode
 
     @property
     def llm_available(self) -> bool:

services/ai/src/ai/main.py

@@ -41,7 +41,7 @@ def init_tracer() -> None:
 
 
 @asynccontextmanager
-async def lifespan(app: FastAPI):
+async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
     """应用生命周期."""
     init_tracer()
     logger.info(
@@ -89,6 +89,12 @@ class ChatResponse(BaseModel):
     degraded: bool = False
 
 
+class QuestionRequest(BaseModel):
+    """题目生成请求."""
+
+    prompt: str
+
+
 def _extract_content(result: dict[str, Any] | None) -> tuple[str, str, dict[str, Any]]:
     """从 OpenAI 响应中抽取 (content, model, usage)。"""
     if result is None:
@@ -171,7 +177,7 @@ async def chat_stream(req: ChatRequest) -> StreamingResponse:
 
 
 @router.post("/generate/question")
-async def generate_question(prompt: str) -> dict[str, Any]:
+async def generate_question(req: QuestionRequest) -> dict[str, Any]:
     """生成题目（无 API key 时降级返回骨架）."""
     with tracer.start_as_current_span("generate_question"):
         messages = [
@@ -180,7 +186,7 @@ async def generate_question(prompt: str) -> dict[str, Any]:
                 "content": "You are an educational question generator. "
                 "Generate a clear, concise question based on the user's prompt.",
             },
-            {"role": "user", "content": prompt},
+            {"role": "user", "content": req.prompt},
         ]
         result = await chat_completion(
             messages=messages,
@@ -190,7 +196,7 @@ async def generate_question(prompt: str) -> dict[str, Any]:
             base_url=settings.openai_base_url,
         )
         if result is None:
-            logger.warning("generate_question_degraded", prompt=prompt[:100])
+            logger.warning("generate_question_degraded", prompt=req.prompt[:100])
             return {
                 "success": True,
                 "data": {"question": "[degraded] question generation skeleton"},