feat: ML tag suggestions, character/fandom integrity, underscores, modal polish

Consolidated merge of feat/tag-suggestions branch. Original 64-commit history
was lost to git-object corruption in a Nextcloud-synced checkout; this single
commit captures the equivalent diff.

Includes:
- pgvector-backed tag suggestion infra (WD14 + SigLIP centroids, ml-worker
  container, Celery tasks, suggestion service, accept/reject endpoints + modal
  UI with green/red chip buttons)
- Character/fandom integrity: title-case normalization on every write path,
  fandom-id backfill, maintenance task + settings button, migrations g26041901
  + h26041901 to canonicalize legacy rows with case-only duplicate merging
- Tag-underscores + modal polish: WD14 name canonicalization at emit + accept
  + add/bulk-add paths, migration i26041901 for legacy-row rename-or-merge
  across character/fandom/NULL kinds, suggestion-accept refresh parity via
  awaited loadTags, persistent chip tint

docker-compose.yml

@@ -15,7 +15,7 @@ services:
 
   # PostgreSQL database
   postgres:
-    image: postgres:16-alpine
+    image: pgvector/pgvector:pg16
     environment:
       POSTGRES_USER: ${DB_USER:-imagerepo}
       POSTGRES_PASSWORD: ${DB_PASS:-postgres}
@@ -105,6 +105,37 @@ services:
         condition: service_healthy
     restart: unless-stopped
 
+  # ML inference worker (CPU-only): WD14 tagging + SigLIP embeddings
+  # Handles: ml queue
+  ml-worker:
+    build:
+      context: .
+      dockerfile: Dockerfile.ml
+    command: celery -A app.celery_app:celery worker --loglevel=info -Q ml --concurrency=1
+    environment:
+      - TZ=${TZ:-America/New_York}
+      - DB_USER=${DB_USER:-imagerepo}
+      - DB_PASS=${DB_PASS:-postgres}
+      - DB_HOST=postgres
+      - DB_PORT=5432
+      - DB_NAME=${DB_NAME:-imagerepo}
+      - CELERY_BROKER_URL=redis://redis:6379/0
+      - CELERY_RESULT_BACKEND=redis://redis:6379/0
+      - ML_MODEL_DIR=/models
+    volumes:
+      - ./imagerepo/images:/images:ro
+    depends_on:
+      postgres:
+        condition: service_healthy
+      redis:
+        condition: service_healthy
+    deploy:
+      resources:
+        limits:
+          cpus: '4.0'
+          memory: 8G
+    restart: unless-stopped
+
 volumes:
   redis_data:
   postgres_data: