feat: jc 引擎主线搬入 app/engine（315 测试基线全绿：320 去掉 admin 5 用例）

Co-Authored-By: Claude Code <noreply@anthropic.com>

app/main.py

@@ -0,0 +1,78 @@
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+from fastapi.staticfiles import StaticFiles
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+
+from app.engine.config import settings, ensure_dirs, STATIC_DIR
+from app.engine.models import Base
+
+
+# 后台推送任务的独立连接写结果可能撞上 SMTP 窗口内持有的写锁,默认 5s
+# 忙等上限低于 SMTP 最坏时长,抬到 30s;等待发生在 aiosqlite 工作线程,不阻塞事件循环
+engine = create_async_engine(settings.DATABASE_URL, echo=settings.APP_DEBUG,
+                             connect_args={"timeout": 30})
+async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+
+
+async def _migrate(conn):
+    result = await conn.execute(text("PRAGMA table_info(conversations)"))
+    columns = {row[1] for row in result}
+    if "page_token" not in columns:
+        await conn.execute(text(
+            "ALTER TABLE conversations ADD COLUMN page_token VARCHAR(64)"
+        ))
+
+    result = await conn.execute(text("PRAGMA table_info(evaluations)"))
+    columns = {row[1] for row in result}
+    if "correction_count" not in columns:
+        await conn.execute(text(
+            "ALTER TABLE evaluations ADD COLUMN correction_count INTEGER DEFAULT 0"
+        ))
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    ensure_dirs()
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+        await _migrate(conn)
+    # 询盘推送(设计 8.2): 清扫崩溃遗留的 stale pending → failed
+    # 函数内导入: lead_push_service 顶部 from app.main import async_session,
+    # 顶层互相导入会循环
+    from app.engine.services.lead_push_service import sweep_stale_pending
+    await sweep_stale_pending()
+    yield
+
+
+app = FastAPI(title="HESUPIPE AI 客服", lifespan=lifespan)
+
+from app.engine.routes.chat import router as chat_router
+from app.engine.routes.chat_rest import router as chat_rest_router
+app.include_router(chat_router)
+app.include_router(chat_rest_router)
+
+app.mount("/static", StaticFiles(directory=str(STATIC_DIR)), name="static")
+
+
+@app.middleware("http")
+async def static_no_cache(request, call_next):
+    """静态资源协商缓存(2026-09-30 线上事件): 无 Cache-Control 时浏览器对
+    widget.js 走启发式缓存,修复部署后用户端仍跑旧脚本。no-cache=每次用
+    etag 轻量协商,有更新即时生效,未变则 304 几乎零开销。"""
+    resp = await call_next(request)
+    if request.url.path.startswith("/static/"):
+        resp.headers["Cache-Control"] = "no-cache"
+    return resp
+
+
+@app.get("/")
+async def index():
+    from fastapi.responses import FileResponse
+    return FileResponse(str(STATIC_DIR / "chat.html"))
+
+
+@app.get("/health")
+async def health():
+    return {"status": "ok"}