docs: README matches current stack and covers ML suggestions

Quick Start had drifted: postgres:16-alpine instead of pgvector/pg16,
a single celery-worker + celery-beat layout instead of the actual
worker / scheduler / ml-worker split, and no mention of the ML
tag-suggestion surface. Updates the compose example to mirror the
real docker-compose.yml, adds ml-worker env vars and /models volume
docs, and documents the ML maintenance tools in Settings.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -10,6 +10,7 @@ A self-hosted image and video gallery application designed for organizing and vi
 - **Video Support** - Playback for video files with automatic transcoding to MP4
 - **Tagging System** - Organize images with tags (artist, character, series, rating, archive, user-defined)
 - **Tag Autocomplete** - Quick tag entry with search suggestions
+- **ML Tag Suggestions** - WD14 tagger + SigLIP embedding centroids propose tags you can accept/reject per image
 - **Automatic Importing** - Celery-based task queue scans `/import` directory on schedule
 - **Archive Extraction** - Supports ZIP, RAR, 7z and other archive formats
 - **Duplicate Detection** - Perceptual hash (pHash) comparison to skip similar images
@@ -35,7 +36,7 @@ services:
       retries: 5
 
   postgres:
-    image: postgres:16-alpine
+    image: pgvector/pgvector:pg16
     environment:
       POSTGRES_USER: imagerepo
       POSTGRES_PASSWORD: your_secure_password
@@ -52,7 +53,7 @@ services:
     image: git.fabledsword.com/bvandeusen/imagerepo:latest
     ports:
       - "5000:5000"
-    environment:
+    environment: &app_env
       - DB_USER=imagerepo
       - DB_PASS=your_secure_password
       - DB_HOST=postgres
@@ -68,16 +69,11 @@ services:
       redis:
         condition: service_healthy
 
-  celery-worker:
+  # Heavy processing: import, thumbnail, sidecar, default queues.
+  worker:
     image: git.fabledsword.com/bvandeusen/imagerepo:latest
-    command: celery -A app.celery_app:celery worker --loglevel=info -Q scan,import,thumbnail,sidecar,default --concurrency=2
-    environment:
-      - DB_USER=imagerepo
-      - DB_PASS=your_secure_password
-      - DB_HOST=postgres
-      - DB_NAME=imagerepo
-      - CELERY_BROKER_URL=redis://redis:6379/0
-      - CELERY_RESULT_BACKEND=redis://redis:6379/0
+    command: celery -A app.celery_app:celery worker --loglevel=info -Q import,thumbnail,sidecar,default --concurrency=2
+    environment: *app_env
     volumes:
       - ./imagerepo/images:/images
       - ./your-media:/import
@@ -87,20 +83,33 @@ services:
       redis:
         condition: service_healthy
 
-  celery-beat:
+  # Beat scheduler + maintenance/scan worker, split off so long imports don't starve periodic tasks.
+  scheduler:
     image: git.fabledsword.com/bvandeusen/imagerepo:latest
-    command: celery -A app.celery_app:celery beat --loglevel=info
-    environment:
-      - DB_USER=imagerepo
-      - DB_PASS=your_secure_password
-      - DB_HOST=postgres
-      - DB_NAME=imagerepo
-      - CELERY_BROKER_URL=redis://redis:6379/0
-      - CELERY_RESULT_BACKEND=redis://redis:6379/0
-      - IMPORT_EVERY_SECONDS=28800
+    command: celery -A app.celery_app:celery worker --beat --loglevel=info -Q maintenance,scan --concurrency=1
+    environment: *app_env
+    volumes:
+      - ./imagerepo/images:/images
+      - ./your-media:/import
     depends_on:
-      - redis
-      - celery-worker
+      postgres:
+        condition: service_healthy
+      redis:
+        condition: service_healthy
+
+  # CPU-only ML inference: WD14 tags + SigLIP embeddings. Models self-heal into ${MODELS_DIR} on start.
+  ml-worker:
+    image: git.fabledsword.com/bvandeusen/imagerepo-ml:latest
+    command: celery -A app.celery_app:celery worker --loglevel=info -Q ml --concurrency=1
+    environment: *app_env
+    volumes:
+      - ./imagerepo/images:/images:ro
+      - ./imagerepo/models:/models
+    depends_on:
+      postgres:
+        condition: service_healthy
+      redis:
+        condition: service_healthy
 
 volumes:
   redis_data:
@@ -114,9 +123,10 @@ Then visit `http://localhost:5000` in your browser.
 ImageRepo uses a task queue architecture for background processing:
 
 - **Web** - Flask application serving the UI and API
-- **Celery Worker** - Processes import, thumbnail, and metadata tasks
-- **Celery Beat** - Schedules periodic tasks (directory scans, recovery)
-- **PostgreSQL** - Primary database for all data
+- **Worker** - Heavy processing: `import`, `thumbnail`, `sidecar`, `default` queues
+- **Scheduler** - Celery Beat + a `maintenance`/`scan` worker (kept separate so long imports don't starve periodic tasks)
+- **ML Worker** - CPU-only WD14 + SigLIP inference on the `ml` queue (separate image, models self-heal on start)
+- **PostgreSQL** - Primary database, uses `pgvector` extension for SigLIP embedding similarity
 - **Redis** - Message broker for Celery task queue
 
 ## Volumes
@@ -125,6 +135,7 @@ ImageRepo uses a task queue architecture for background processing:
 |------|-------------|
 | `/images` | Where imported images and thumbnails are stored |
 | `/import` | Source directory the importer scans for new media |
+| `/models` | ml-worker only — WD14 + SigLIP weights (~4 GB, fetched on first start) |
 
 ## Environment Variables
 
@@ -176,6 +187,16 @@ These can also be configured via the Settings page in the UI.
 | `ARCHIVE_MIN_FREE_GB` | `0` | Minimum free disk space (GB) required to start extraction (0 = disabled) |
 | `ARCHIVE_NUM_WIDTH` | `4` | Zero-padding width for archive sequence numbers in tags |
 
+### ML Tag Suggestions (ml-worker only)
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `ML_MODEL_DIR` | `/models` | Where WD14 + SigLIP weights are written/read |
+| `WD14_REPO` | `SmilingWolf/wd-eva02-large-tagger-v3` | HuggingFace repo for the WD14 tagger |
+| `SIGLIP_REPO` | `google/siglip-so400m-patch14-384` | HuggingFace repo for the SigLIP encoder |
+| `WD14_REVISION` | (latest) | Pin WD14 to a specific commit SHA |
+| `SIGLIP_REVISION` | (latest) | Pin SigLIP to a specific commit SHA |
+
 ### Other
 
 | Variable | Default | Description |
@@ -227,6 +248,11 @@ The Settings page (`/settings`) provides:
 - **Find Duplicates** - Scan for visually similar images using pHash
 - **Reset Image Database** - Clear all image records (files remain on disk)
 
+### ML Maintenance Tools
+- **Run ML backfill** - Enqueue `tag_and_embed` for every image missing predictions or embeddings for the current model versions. Safe to re-run; paginates forward and drops already-processed images. Expected runtime on a fresh DB: hours to days on a single ml-worker.
+- **Recompute all centroids** - Rebuild per-tag SigLIP centroids from current image tags. Run after the initial backfill drains, or whenever bulk manual tagging has drifted suggestions.
+- **Sync character fandoms** - Additively re-apply each character's fandom tag to every image already tagged with that character. Never removes existing fandom tags.
+
 ### Import Filters
 Configure filtering rules that apply during import:
 - Minimum dimensions