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

scripts/download_models.py

@@ -0,0 +1,45 @@
+"""Pre-fetch WD14 and SigLIP model files into $ML_MODEL_DIR at image build time."""
+from __future__ import annotations
+import os
+import sys
+
+from huggingface_hub import hf_hub_download, snapshot_download
+
+MODEL_DIR = os.environ.get('ML_MODEL_DIR', '/models')
+WD14_REPO = os.environ.get('WD14_REPO', 'SmilingWolf/wd-eva02-large-tagger-v3')
+SIGLIP_REPO = os.environ.get('SIGLIP_REPO', 'google/siglip-so400m-patch14-384')
+
+
+def download_wd14() -> None:
+    target = os.path.join(MODEL_DIR, 'wd14')
+    os.makedirs(target, exist_ok=True)
+    hf_hub_download(repo_id=WD14_REPO, filename='model.onnx', local_dir=target, local_dir_use_symlinks=False)
+    hf_hub_download(repo_id=WD14_REPO, filename='selected_tags.csv', local_dir=target, local_dir_use_symlinks=False)
+    print(f"WD14 downloaded to {target}")
+
+
+def download_siglip() -> None:
+    target = os.path.join(MODEL_DIR, 'siglip')
+    os.makedirs(target, exist_ok=True)
+    snapshot_download(
+        repo_id=SIGLIP_REPO,
+        local_dir=target,
+        local_dir_use_symlinks=False,
+        allow_patterns=[
+            'config.json',
+            'preprocessor_config.json',
+            'tokenizer_config.json',
+            'tokenizer.json',
+            'special_tokens_map.json',
+            'spiece.model',
+            'model.safetensors',
+            'pytorch_model.bin',
+        ],
+    )
+    print(f"SigLIP downloaded to {target}")
+
+
+if __name__ == '__main__':
+    download_wd14()
+    download_siglip()
+    sys.exit(0)