feat: add A-share and HK stock data via AKShare (TDD)

5 new endpoints under /api/v1/cn/:
- GET /cn/a-share/{symbol}/quote - A-share real-time quote
- GET /cn/a-share/{symbol}/historical - A-share historical OHLCV
- GET /cn/a-share/search?query= - search A-shares by name
- GET /cn/hk/{symbol}/quote - HK stock real-time quote
- GET /cn/hk/{symbol}/historical - HK stock historical OHLCV

Features:
- Chinese column names auto-mapped to English
- Symbol validation: A-share ^[036]\d{5}$, HK ^\d{5}$
- qfq (forward-adjusted) prices by default
- 79 new tests (51 service unit + 28 route integration)
- All 470 tests passing

routes_cn.py

@@ -0,0 +1,105 @@
+"""Routes for A-share (China) and Hong Kong stock market data via AKShare."""
+
+from fastapi import APIRouter, HTTPException, Path, Query
+
+from models import ApiResponse
+from route_utils import safe
+import akshare_service
+
+router = APIRouter(prefix="/api/v1/cn", tags=["China & HK Markets"])
+
+
+# --- Validation helpers ---
+
+
+def _validate_a_share(symbol: str) -> str:
+    """Validate A-share symbol format; raise 400 on failure."""
+    if not akshare_service.validate_a_share_symbol(symbol):
+        raise HTTPException(
+            status_code=400,
+            detail=(
+                f"Invalid A-share symbol '{symbol}'. "
+                "Must be 6 digits starting with 0, 3, or 6 (e.g. 000001, 300001, 600519)."
+            ),
+        )
+    return symbol
+
+
+def _validate_hk(symbol: str) -> str:
+    """Validate HK stock symbol format; raise 400 on failure."""
+    if not akshare_service.validate_hk_symbol(symbol):
+        raise HTTPException(
+            status_code=400,
+            detail=(
+                f"Invalid HK symbol '{symbol}'. "
+                "Must be exactly 5 digits (e.g. 00700, 09988)."
+            ),
+        )
+    return symbol
+
+
+# --- A-share routes ---
+# NOTE: /a-share/search MUST be registered before /a-share/{symbol} to avoid shadowing.
+
+
+@router.get("/a-share/search", response_model=ApiResponse)
+@safe
+async def a_share_search(
+    query: str = Query(..., description="Stock name to search for (partial match)"),
+) -> ApiResponse:
+    """Search A-share stocks by name (partial match)."""
+    data = await akshare_service.search_a_shares(query)
+    return ApiResponse(data=data)
+
+
+@router.get("/a-share/{symbol}/quote", response_model=ApiResponse)
+@safe
+async def a_share_quote(
+    symbol: str = Path(..., min_length=6, max_length=6),
+) -> ApiResponse:
+    """Get real-time A-share quote (沪深 real-time price)."""
+    symbol = _validate_a_share(symbol)
+    data = await akshare_service.get_a_share_quote(symbol)
+    if data is None:
+        raise HTTPException(status_code=404, detail=f"A-share symbol '{symbol}' not found.")
+    return ApiResponse(data=data)
+
+
+@router.get("/a-share/{symbol}/historical", response_model=ApiResponse)
+@safe
+async def a_share_historical(
+    symbol: str = Path(..., min_length=6, max_length=6),
+    days: int = Query(default=365, ge=1, le=3650),
+) -> ApiResponse:
+    """Get A-share daily OHLCV history with qfq (前复权) adjustment."""
+    symbol = _validate_a_share(symbol)
+    data = await akshare_service.get_a_share_historical(symbol, days=days)
+    return ApiResponse(data=data)
+
+
+# --- HK stock routes ---
+
+
+@router.get("/hk/{symbol}/quote", response_model=ApiResponse)
+@safe
+async def hk_quote(
+    symbol: str = Path(..., min_length=5, max_length=5),
+) -> ApiResponse:
+    """Get real-time HK stock quote (港股 real-time price)."""
+    symbol = _validate_hk(symbol)
+    data = await akshare_service.get_hk_quote(symbol)
+    if data is None:
+        raise HTTPException(status_code=404, detail=f"HK symbol '{symbol}' not found.")
+    return ApiResponse(data=data)
+
+
+@router.get("/hk/{symbol}/historical", response_model=ApiResponse)
+@safe
+async def hk_historical(
+    symbol: str = Path(..., min_length=5, max_length=5),
+    days: int = Query(default=365, ge=1, le=3650),
+) -> ApiResponse:
+    """Get HK stock daily OHLCV history with qfq adjustment."""
+    symbol = _validate_hk(symbol)
+    data = await akshare_service.get_hk_historical(symbol, days=days)
+    return ApiResponse(data=data)