fix: resolve startup NameError in vector-sync metrics task

The Starlette lifespan started `vector_sync_metrics_task` with undefined
names `task_producer` and `receive_stream`. Those locals only exist inside
the `_wire_vector_sync_state` helper; in the lifespan the transport is bound
as `ingest_transport`. The undefined reference raised `NameError`, which
aborted the background-sync task group and crashed startup in every
deployment mode ("Application startup failed. Exiting.").

Introduced by fbe70ecd ("feat: backend-agnostic vector-sync gauges").

Pass `ingest_transport.producer` / `ingest_transport.receive_stream` at both
call sites (single-user app.py:1791, OAuth/login-flow app.py:2012).

Also fix 10 pre-existing `ty` possibly-missing-attribute diagnostics: the
deck indexing code in scanner.py, processor.py and search/context.py reads
full-DeckCard-only fields (description, type, owner, etag, lastModified) off
`stack.cards`, typed `list[DeckCard | DeckCardSummary]`. Freshly-fetched
stacks from `get_stacks()` always hold full DeckCards (the summary
projection only happens in the tool layer), so narrow with
`cast(list[DeckCard], ...)` — matching the existing pattern in
server/deck.py.

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

nextcloud_mcp_server/app.py

@@ -1790,8 +1790,8 @@ def get_app(transport: str = "streamable-http", enabled_apps: list[str] | None =
                 # falls back to the procrastinate job counts there.
                 await tg.start(
                     vector_sync_metrics_task,
-                    task_producer,
-                    receive_stream,
+                    ingest_transport.producer,
+                    ingest_transport.receive_stream,
                     shutdown_event,
                 )
 
@@ -2011,8 +2011,8 @@ def get_app(transport: str = "streamable-http", enabled_apps: list[str] | None =
                     # falls back to the procrastinate job counts there.
                     await tg.start(
                         vector_sync_metrics_task,
-                        task_producer,
-                        receive_stream,
+                        ingest_transport.producer,
+                        ingest_transport.receive_stream,
                         shutdown_event,
                     )