V4.6 Phase 1: deletions and quick wins

Pure remediation; no behavior change. Every item traces to a finding in
docs/architecture_code_review_2026-08-17.md.

Deletions
- Delete app_state.py, which had zero importers and whose get_session_factory
  raised TypeError at runtime [HIGH-01].
- Delete services/transcription.py and point build_prompt_execution imports at
  services/sources.py; drop the store.py compatibility aliases [MED-05].
- Delete ServiceBase.queue and its unparameterized asyncio.Queue [MED-07].
- Delete db/operations.get_next_queued_job, a divergent duplicate [CRIT-01].
- Drop the discarded load_docs parameter from list_jobs [LOW-03].

Config
- Delete worker_retry_backoff_seconds; no backoff behavior existed anywhere, so
  wiring it would have been a new feature [MED-02].
- Wire sqlite_check_same_thread through get_engine. The engine hardcoded the
  setting's own default, so this preserves behavior exactly [MED-02].
- Replace DATABASE_URL in docker-compose.yml with the nested DATABASE__DRIVER /
  DATABASE__PATH names. Settings uses env_nested_delimiter with extra="ignore",
  so DATABASE_URL was silently discarded [MED-10].

UI
- Move the 23KB inline VIBESCRIBE_LOGO_SVG to ui/static/vibescribe_logo.svg and
  load it through a cached read_svg sibling of read_css [MED-09].
- Route the portrait upload failure through error_presenter.show_error [LOW-07].
- Cancel the job detail auto-refresh timer instead of only deactivating it, and
  name its interval constant [LOW-06].

Worker
- Make WorkerNotifier runtime_checkable and validate the resolved object in
  resolve_worker_notifier, which previously returned any non-None attribute
  unchecked [LOW-04].

Docs and lint
- Fix two stale paths in services.instructions.md, one of which pointed at the
  module deleted here [LOW-02].
- ruff check --fix to zero [LOW-01].

Verified: 264 passed, 4 skipped; ruff check clean.

Co-authored-by: Copilot App <[email protected]>

.github/instructions/services.instructions.md

@@ -7,7 +7,7 @@ applyTo: 'src/transcription/services/*.py'
 
 ## Structure
 
-- Project core data models defined in [models](../../src/transcription/models.py)
+- Project core data models defined in [models](../../src/transcription/db/models.py)
 - 1 service class per data model
 - Only services directly interact with the database, and only through async methods
 - Services are completely independent of one another. Any operation that needs to use more than a single service, which is most of them, needs to have a separate orchestration function.
@@ -15,7 +15,7 @@ applyTo: 'src/transcription/services/*.py'
 ## Error Handling
 
 - Service-specific errors defined at the top of the respective module and inherit from `AppError`
-- Use a context manager for large `try/except` blocks like in [transcription](../../src/transcription/services/transcription.py)
+- Use a context manager for large `try/except` blocks like `handle_transcription_errors` in [sources](../../src/transcription/services/sources.py)
 
 ## Checklist