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/alembic/versions/0019_drop_ai_remnants.py

@@ -0,0 +1,47 @@
+"""Drop AI remnants: photos.needs_review and the pgvector extension
+
+Revision ID: 0019_drop_ai_remnants
+Revises: 0018_photos_nextcloud_fileid
+Create Date: 2026-05-14
+
+The vision pipeline has been removed entirely (no more classifier, no
+worker-vision service, no torch/onnxruntime/open-clip-torch deps). The
+`needs_review` boolean and its partial index were populated only by
+that classifier and have no remaining writers or readers.
+
+The pgvector extension was originally added by 0003_pgvector_embeddings
+for the embeddings table that 0012_strip_ai_pipeline dropped; the
+extension itself is now unused, and the next deploy switches the
+Postgres image from pgvector/pgvector:pg16 to plain postgres:16. The
+extension must be dropped *before* that image swap or the new
+container will fail to load existing CREATE EXTENSION declarations.
+"""
+from typing import Sequence, Union
+
+from alembic import op
+
+
+revision: str = "0019_drop_ai_remnants"
+down_revision: Union[str, None] = "0018_photos_nextcloud_fileid"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.execute("DROP INDEX IF EXISTS ix_photos_needs_review")
+    op.execute("ALTER TABLE photos DROP COLUMN IF EXISTS needs_review")
+    op.execute("DROP EXTENSION IF EXISTS vector")
+
+
+def downgrade() -> None:
+    # Re-create the column as a no-op (data is gone). The pgvector
+    # extension is intentionally NOT re-added — matches the precedent
+    # set by 0012_strip_ai_pipeline for its dropped tables.
+    op.execute(
+        "ALTER TABLE photos ADD COLUMN IF NOT EXISTS needs_review "
+        "BOOLEAN NOT NULL DEFAULT FALSE"
+    )
+    op.execute(
+        "CREATE INDEX IF NOT EXISTS ix_photos_needs_review "
+        "ON photos(needs_review) WHERE needs_review"
+    )