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/static/js/i18n.js

@@ -9,6 +9,7 @@ var I18N = {
     'pos': 'Punto de Venta',
     'catalog': 'Catalogo',
     'inventory': 'Inventario',
+    'diagrams': 'Diagramas',
     'customers': 'Clientes',
     'invoicing': 'Facturacion',
     'accounting': 'Contabilidad',
@@ -164,6 +165,7 @@ var I18N = {
     'pos': 'Point of Sale',
     'catalog': 'Catalog',
     'inventory': 'Inventory',
+    'diagrams': 'Diagrams',
     'customers': 'Customers',
     'invoicing': 'Invoicing',
     'accounting': 'Accounting',