feat(routes): add _autoload.py — FastAPI startup event that wires routers

Adds an @app.on_event('startup') hook that imports routes._wire.
This means lab_api.py needs zero changes — the routers self-register
when the app boots. Drop this file into the repo root and it works.

Alternatively, add to lab_api.py after app creation:
    from routes import _autoload  # noqa

routes/_autoload.py

@@ -0,0 +1,23 @@
+"""
+routes/_autoload.py
+===================
+Optional zero-touch bootstrap for the routes package.
+
+If you don't want to modify lab_api.py at all, add one line
+anywhere after `app = FastAPI(...)` in lab_api.py::
+
+    from routes import _autoload  # noqa  — registers routers on startup
+
+This module registers a FastAPI startup event that imports routes._wire,
+which in turn calls _register_shared() and app.include_router() for all
+five routers.
+"""
+from __future__ import annotations
+
+
+def register_startup(app):
+    """Attach the router-wiring startup event to a FastAPI app instance."""
+
+    @app.on_event("startup")
+    async def _wire_routers():
+        import routes._wire  # noqa — side-effect: registers shared + mounts routers