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/sidebar.js

@@ -23,6 +23,7 @@
             { name: _t('pos'), href: '/pos/sale', icon: '<rect x="2" y="3" width="20" height="14" rx="2"/><path d="M8 21h8M12 17v4"/>' },
             { name: _t('catalog'), href: '/pos/catalog', icon: '<path d="M4 6h16M4 10h16M4 14h16M4 18h16"/>' },
             { name: _t('inventory'), href: '/pos/inventory', icon: '<path d="M21 16V8a2 2 0 0 0-1-1.73l-7-4a2 2 0 0 0-2 0l-7 4A2 2 0 0 0 3 8v8a2 2 0 0 0 1 1.73l7 4a2 2 0 0 0 2 0l7-4A2 2 0 0 0 21 16z"/><polyline points="3.27 6.96 12 12.01 20.73 6.96"/><line x1="12" y1="22.08" x2="12" y2="12"/>' },
+            { name: _t('diagrams'), href: '/pos/diagrams', icon: '<path d="M14.7 6.3a1 1 0 0 0 0 1.4l1.6 1.6a1 1 0 0 0 1.4 0l3.77-3.77a6 6 0 0 1-7.94 7.94l-6.91 6.91a2.12 2.12 0 0 1-3-3l6.91-6.91a6 6 0 0 1 7.94-7.94l-3.76 3.76z"/>' },
         ]},
         { label: _t('nav_management'), items: [
             { name: _t('customers'), href: '/pos/customers', icon: '<path d="M17 21v-2a4 4 0 0 0-4-4H5a4 4 0 0 0-4 4v2"/><circle cx="9" cy="7" r="4"/><path d="M23 21v-2a4 4 0 0 0-3-3.87M16 3.13a4 4 0 0 1 0 7.75"/>' },