refactor(vector-sync): clear SonarCloud gate + round-2 nits

Quality-gate fixes (new-code conditions on PR #902):
- new_security_hotspots_reviewed: drop the fake "http://nextcloud" host in the
  manager tests to https:// (python:S5332 ×2).
- new_security_rating: generate the integration test's fake app password with
  secrets.token_urlsafe instead of a hardcoded literal (python:S2068).
- new_reliability_rating: restructure the user_manager sleep so an explicit
  await checkpoint lives inside the cancellation scope — await one waiter
  directly while watching shutdown via start_soon (python:S7490). Behaviour is
  unchanged: timeout, shutdown, or a provisioning ring all end the sleep.

Review nits:
- Move the shutdown test's fail_after(2) to wrap the whole task group so it
  actually bounds the task-group exit (was guarding a no-op sleep); drop the
  sleep(0) stub (python:S7491).
- Type _wake_on's wait_fn as Callable[[], Awaitable[object]].
- Note in _wire_vector_sync_state why provision_signal is set on the singleton
  only, not fanned out to app.state.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/unit/vector/test_user_manager_provision_wake.py

@@ -134,7 +134,7 @@ async def test_user_manager_wakes_on_provision_signal(mocker):
             shutdown_event,
             scanner_wake_event,
             storage,
-            "http://nextcloud",
+            "https://nextcloud",
             user_states,
             tg,
             provision_signal,
@@ -163,32 +163,36 @@ async def test_user_manager_shutdown_still_breaks_sleep(mocker):
     mocker.patch(
         "nextcloud_mcp_server.vector.oauth_sync.get_settings", return_value=settings
     )
+
+    async def _unused_scanner(*args, **kwargs):
+        # No users provisioned, so this is never called; keep a harmless stub.
+        return None
+
     mocker.patch(
         "nextcloud_mcp_server.vector.oauth_sync._run_user_scanner_with_scope",
-        # No users provisioned, so this is never called; keep a harmless stub.
-        lambda *a, **k: anyio.sleep(0),
+        _unused_scanner,
     )
 
     storage = _FakeStorage(set())
     shutdown_event = anyio.Event()
 
-    async with anyio.create_task_group() as tg:
-        await tg.start(
-            user_manager_task,
-            None,
-            shutdown_event,
-            anyio.Event(),
-            storage,
-            "http://nextcloud",
-            {},
-            tg,
-            ProvisionSignal(),
-        )
-        await anyio.sleep(0.05)  # let it enter the sleep
-        shutdown_event.set()
-        # If shutdown didn't break the 1000s sleep, fail_after would trip.
-        with anyio.fail_after(2):
-            await anyio.sleep(0)  # task group exit below is the real assertion
+    # fail_after wraps the whole task group: if shutdown_event doesn't break the
+    # 1000s sleep, the task group never exits and the 2s deadline trips.
+    with anyio.fail_after(2):
+        async with anyio.create_task_group() as tg:
+            await tg.start(
+                user_manager_task,
+                None,
+                shutdown_event,
+                anyio.Event(),
+                storage,
+                "https://nextcloud",
+                {},
+                tg,
+                ProvisionSignal(),
+            )
+            await anyio.sleep(0.05)  # let it enter the sleep
+            shutdown_event.set()
 
 
 # ── notify_user_provisioned no-op guard ──────────────────────────────────────