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>

templates/looks/index.html

@@ -73,8 +73,8 @@
                 {% set lora_name = look.data.lora.lora_name.split('/')[-1].replace('.safetensors', '') %}
                 <small class="text-muted text-truncate" title="{{ look.data.lora.lora_name }}">{{ lora_name }}</small>
                 {% else %}<span></span>{% endif %}
-                <button class="btn btn-sm btn-outline-danger py-0 px-1 flex-shrink-0 ms-1 resource-delete-btn" title="Delete"
-                        data-category="looks" data-slug="{{ look.slug }}" data-name="{{ look.name | e }}">🗑</button>
+                <button class="btn btn-sm btn-danger py-0 px-1 flex-shrink-0 ms-1 resource-delete-btn" title="Delete"
+                        data-category="looks" data-slug="{{ look.slug }}" data-name="{{ look.name | e }}"><img src="/static/icons/trash.png" alt="Delete" style="width:16px;height:16px;"></button>
             </div>
         </div>
     </div>