Major refactor: deduplicate routes, sync, JS, and fix bugs

- Extract 8 common route patterns into factory functions in routes/shared.py
  (favourite, upload, replace cover, save defaults, clone, save JSON,
  get missing, clear covers) — removes ~1,100 lines across 9 route files
- Extract generic _sync_category() in sync.py — 7 sync functions become
  one-liner wrappers, removing ~350 lines
- Extract shared detail page JS into static/js/detail-common.js — all 9
  detail templates now call initDetailPage() with minimal config
- Extract layout inline JS into static/js/layout-utils.js (~185 lines)
- Extract library toolbar JS into static/js/library-toolbar.js
- Fix finalize missing-image bug: raise RuntimeError instead of logging
  warning so job is marked failed
- Fix missing scheduler default in _default_checkpoint_data()
- Fix N+1 query in Character.get_available_outfits() with batch IN query
- Convert all print() to logger across services and routes
- Add missing tags display to styles, scenes, detailers, checkpoints detail
- Update delete buttons to use trash.png icon with solid red background
- Update CLAUDE.md to reflect new architecture

Net reduction: ~1,600 lines

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

models.py

@@ -65,8 +65,10 @@ class Character(db.Model):
         
         # Add assigned outfits from Outfit table
         if self.assigned_outfit_ids:
+            assigned = Outfit.query.filter(Outfit.outfit_id.in_(self.assigned_outfit_ids)).all()
+            outfit_by_id = {o.outfit_id: o for o in assigned}
             for outfit_id in self.assigned_outfit_ids:
-                outfit = Outfit.query.filter_by(outfit_id=outfit_id).first()
+                outfit = outfit_by_id.get(outfit_id)
                 if outfit:
                     outfits.append({
                         'outfit_id': outfit.outfit_id,