refactor: use shared ServiceLink blueprint

- Replace the local /rpc Quart route with the shared ServiceLink blueprint helper.
- Move mesh scope enforcement into bearer_verifier via require_scope.
- Update ServiceLink tests to call the public handle_envelope and verify exports.
- Advance the servicelink submodule to include the shared CLI and RPC discovery work.

tests/test_servicelink_link.py

@@ -9,7 +9,7 @@ sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
 
 from quart import Quart
 
-from servicelink import Request
+from servicelink import Request, handle_envelope
 
 # Load routes/api/link.py in isolation. Importing it as `routes.api.link` would
 # run routes/__init__.py -> my_modules.app.setup -> constens (asyncio.run at
@@ -63,11 +63,11 @@ def _call(envelope, token=None):
     app = Quart(__name__)
     app.convex = FakeConvex()
     async with app.test_request_context('/rpc', method='POST'):
-      status, body, _ = await link.handle_envelope(
+      status, body, _ = await handle_envelope(
         link.router,
         json.dumps(envelope).encode('utf-8'),
         authorization=f'Bearer {token}' if token else None,
-        verify=link._verify,
+        verify=link.verify,
         content_type='application/json',
       )
     return status, json.loads(body)