refactor: drop AI/vision pipeline + plain Postgres + full-refresh script

Removes the OpenCLIP-on-ONNX classifier and everything that fed or
consumed it:
  - backend: app/services/vision/, app/tasks/vision.py,
    app/services/feature_flags.py, app/routers/features.py — all
    deleted; admin AI/feature-flag endpoints and the worker-vision
    bootstrap call gone. Photo.needs_review and its index dropped.
  - frontend: AI Settings tab, useFeaturesQuery hook, FeatureFlag
    types, "Needs Review" sidebar entry + filter, needs_review filter
    URL param all gone.
  - infra: worker-vision compose service + models_data volume deleted;
    worker-light command no longer runs bootstrap_models; the db
    image switches from pgvector/pgvector:pg16 to postgres:16; backend
    Dockerfile drops the dedicated torch RUN layer; requirements.txt
    drops torch/torchvision/open-clip-torch/onnxruntime.

Alembic 0019_drop_ai_remnants:
  - drops photos.needs_review + ix_photos_needs_review
  - DROP EXTENSION IF EXISTS vector (must run before the image swap;
    the new postgres:16 doesn't ship pgvector)

New scripts/full_refresh.py: one-shot DB ↔ filesystem reconciliation.
Runs cleanup_data_integrity, scans every active SourceRoot inline
(no celery dependency so the worker can be stopped), hard-prunes
photo + folder rows for files that are gone, removes orphan
/data/thumbs/{user}/{photo}/ directories. New helper
prune_orphan_thumbnails in cleanup.py.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/routers/photos.py

@@ -73,7 +73,6 @@ async def list_photos(
     color_label: Optional[str] = None,
     is_discarded: Optional[bool] = False,
     is_duplicate: Optional[bool] = None,
-    needs_review: Optional[bool] = None,
     has_date_warning: Optional[bool] = None,
     heap_id: Optional[str] = None,
     sort: str = "taken_at",
@@ -244,8 +243,6 @@ async def list_photos(
     # view shows everything regardless of duplicate status.
     if is_duplicate is not None:
         filters.append(Photo.is_duplicate == is_duplicate)
-    if needs_review is not None:
-        filters.append(Photo.needs_review == needs_review)
     if has_date_warning is not None:
         filters.append(Photo.has_date_warning == has_date_warning)