feat(pos): add exploded diagrams feature (#9) with interactive SVG viewer

- Blueprint with API endpoints: list, detail, SVG serve, vehicle-linked diagrams
- Interactive SVG viewer with zoom/pan (mouse wheel, drag, touch, keyboard)
- Clickable hotspots that highlight on hover and show part detail panel
- Parts sidebar listing all callout numbers with catalog search integration
- 3 placeholder SVG diagrams: braking system, suspension, engine components
- Seeded diagrams, hotspots, and vehicle_diagrams in DB
- Added to sidebar nav, i18n (ES/EN), and "Ver diagramas" link in catalog

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pos/app.py

@@ -54,6 +54,9 @@ def create_app():
     from blueprints.marketplace_bp import marketplace_bp
     app.register_blueprint(marketplace_bp)
 
+    from blueprints.diagrams_bp import diagrams_bp
+    app.register_blueprint(diagrams_bp)
+
     # Health check
     @app.route('/pos/health')
     def health():
@@ -120,6 +123,10 @@ def create_app():
     def pos_marketplace():
         return render_template('marketplace.html')
 
+    @app.route('/pos/diagrams')
+    def pos_diagrams():
+        return render_template('diagrams.html')
+
     @app.route('/pos/static/<path:filename>')
     def pos_static(filename):
         return send_from_directory('static', filename)