perf(services): keep only the shared startup inventory read (J1)

Drop the startup deferral gate, its kill switch and the deferred loads:
they lowered renderer.ipcCallsToFirstCard but moved neither
spawnToFirstCardMs nor load->card beyond drift, and they grew
renderer.initialBytes. Keep the shared in-flight inventory read, inline
it in PlaylistsService with short property names, and copy the joiner's
result with structuredClone (the Electron renderer has it; the services
test setup polyfills it for jsdom).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/development/electron-debugging.md

@@ -34,7 +34,6 @@ IPTVNATOR_TRACE_STARTUP=1 pnpm nx serve electron-backend
     - `IPTVNATOR_PERF_COUNT_SQL=1`, together with `IPTVNATOR_PERF_CAPTURE=1`, also counts every SQL statement of the main-process and database-worker connections for `main.sqlStatementsBeforeReadyToShow`; it wraps each statement execution, including every row of a bulk insert, so only the launch journey sets it and the import benchmarks leave it unset
     - `IPTVNATOR_PERF_WORKER_PROFILING=1` enables development/test-only, request-scoped worker receive/work/response-post timestamps, thread CPU, event-loop utilization/delay, count-only playlist serialization/SQLite write/read/deserialization plus Xtream category/content/cache-clear/delete/in-source-search phase events, profiling-only worker cancel-receipt acknowledgements, valid-sample-counted isolate peak memory, and the database worker's idle-only one-shot post-GC heap probe; overlapping database requests are explicitly invalidated instead of misattributed, the performance benchmark sets the flag automatically, and production launches must leave it unset
     - `IPTVNATOR_DISABLE_COMPILE_CACHE=1` disables the main-process V8 compile cache; `IPTVNATOR_COMPILE_CACHE_DIR=<dir>` relocates it. The startup trace reports the outcome as `compile-cache`
-    - `IPTVNATOR_DISABLE_STARTUP_DEFERRAL=1` starts the renderer's startup gate open, so the download list, update status and dashboard recent/favorites reads run before the first screen again (kill switch; see "Startup work before the first card" in `docs/architecture/performance-journeys.md`)
 
 - Settings, portal request/response, and trace payloads must use
   `@iptvnator/shared/logging` or the redacting portal logger before reaching