fix(observability): bump quart_common and refresh stale error tests

- Bump quart_common to 53b7599 with the httpx request-less crash fix
- The global exception handler no longer dies on RequestError without request
- Expect 503 for Convex connect failures, 504 is reserved for timeouts
- Add an API timeout case so the 504 branch stays covered
- Register a link_composer blueprint so error.htm can render its navigation
- Move the legacy logger assertion into a WIDE_EVENT_ENABLED=false test
- Assert user.session_age_seconds instead of the removed session.age_seconds
- Expect no legacy middleware logs while wide-event logging is active

The middleware moved into quart_common's register_security_middleware, so the
NanoShare copies of those assertions had been describing pre-refactor
behaviour. Suite is green again at 141 passed.

tests/test_wide_event_nanoshare.py

@@ -98,7 +98,8 @@ def test_middleware_adds_user_and_client_context(monkeypatch):
       assert "authenticated" not in g.wide_event["session"]
       assert g.wide_event["session"]["permanent"] is True
       assert g.wide_event["session"]["login_at_unix"] == 1
-      assert g.wide_event["session"]["age_seconds"] >= 0
+      assert "age_seconds" not in g.wide_event["session"]
+      assert g.wide_event["user"]["session_age_seconds"] >= 0
       assert g.wide_event["client"]["ip"] == "203.0.113.10"
 
   asyncio.run(run_test())
@@ -143,6 +144,6 @@ def test_middleware_records_convex_security_failures(monkeypatch):
       assert g.wide_event["client"]["ip"] == "203.0.113.12"
       assert g.wide_event["security"] == {"ip_lookup_failed": True}
       assert g.wide_event["error"]["type"] == "RuntimeError"
-      assert fake_logger.records == [("error", "[MIDDLEWARE] Convex ip_lookup failed: convex down")]
+      assert fake_logger.records == []
 
   asyncio.run(run_test())