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>

routes/strengths.py

@@ -263,7 +263,7 @@ def register_routes(app):
             else:
                 character = None
 
-            print(f"[Strengths] char_slug={char_slug!r} → character={character.slug if character else 'none'}")
+            logger.debug("Strengths: char_slug=%r -> character=%s", char_slug, character.slug if character else 'none')
 
             action_obj = None
             extra_positive = ''
@@ -274,7 +274,7 @@ def register_routes(app):
                     action_obj = Action.query.filter_by(slug=action_slug).first()
                 extra_positive = session.get(f'extra_pos_detailer_{slug}', '')
                 extra_negative = session.get(f'extra_neg_detailer_{slug}', '')
-                print(f"[Strengths] detailer session — char={char_slug}, action={action_slug}, extra_pos={bool(extra_positive)}, extra_neg={bool(extra_negative)}")
+                logger.debug("Strengths: detailer session -- char=%s, action=%s, extra_pos=%s, extra_neg=%s", char_slug, action_slug, bool(extra_positive), bool(extra_negative))
 
             prompts = _build_strengths_prompts(category, entity, character,
                                                action=action_obj, extra_positive=extra_positive)
@@ -321,7 +321,7 @@ def register_routes(app):
             return {'status': 'queued', 'job_id': job['id']}
 
         except Exception as e:
-            print(f"[Strengths] generate error: {e}")
+            logger.exception("Strengths generate error: %s", e)
             return {'error': str(e)}, 500
 
     @app.route('/strengths/<category>/<path:slug>/list')