feat(routes): 迁移播客查询端点（parse/programs/search/hot）

- web/routers/podcast.py：四个播客端点迁至 /api/v1/*，与 Flask 逐字段对齐
- podcast_api 仍为同步模块，用 asyncio.to_thread 包装：阻塞上游不占事件循环，
  行为与 Flask 一致
- 单集解析附音频直链（音质自动降级）+ 解析操作记共享 REQ_LOG

契约奇偶校验：19 项全 OK（新增 podcast hot/search/programs）；
play_count 加入易变字段（上游实时收听计数每次请求都变，非契约漂移）。

验证：pytest 46/46；ruff All checks passed；pyright 0 errors；冒烟 10/10。

web/app.py

@@ -23,6 +23,7 @@ from web.errors import install_error_handlers
 from web.middleware import ResponseHygieneMiddleware
 from web.routers import account as account_router
 from web.routers import music as music_router
+from web.routers import podcast as podcast_router
 from web.routers import site as site_router
 from web.routers import system as system_router
 
@@ -71,6 +72,7 @@ def create_app(serve_flask_fallback: bool = False) -> FastAPI:
     app.include_router(site_router.router, prefix='/api/v1', tags=['site'])
     app.include_router(music_router.router, prefix='/api/v1', tags=['music'])
     app.include_router(account_router.router, prefix='/api/v1', tags=['account'])
+    app.include_router(podcast_router.router, prefix='/api/v1', tags=['podcast'])
 
     install_error_handlers(app)