Fabric.js design canvas implementation and supporting infrastructure

Design Canvas (Primary)
- FabricDesignCanvasV2: Fabric.js-based product customization canvas
  - Lazy-loads Fabric.js to minimize bundle impact
  - Renders product mockup with print area guide (magenta dashed box)
  - Supports front/back view switching with correct product images
  - Color swatch selection for garment customization
  - Text element creation with selection handles and transform controls
  - Fixed React dependency array to prevent infinite renders

Support Components
- DesignCanvasWrapper: Client-side wrapper for SSR compatibility
- DesignCanvasErrorBoundary: Error boundary for canvas failures
- ThemeInitializer: Theme detection and application

Configuration
- Updated .claude/launch.json with dev server settings
- Updated .claude/settings.local.json with local preferences
- Updated next.config.mjs for production build optimization
- Dependency updates in package.json and package-lock.json

Known Issues & TODO
- Image element rendering disabled (Fabric.js compatibility investigation)
- Text editing UI controls needed (font, size, color pickers)
- Delete/undo functionality pending
- Print area alignment needs visual verification
- "Add to Cart" integration with design serialization pending

Testing Artifacts
- check_*.js: Product verification scripts for debugging

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

next.config.mjs

@@ -1,9 +1,8 @@
 /** @type {import('next').NextConfig} */
 const nextConfig = {
   reactStrictMode: true,
-  eslint: { ignoreDuringBuilds: true },
+  serverExternalPackages: ['@prisma/client'],
   experimental: {
-    serverComponentsExternalPackages: ['@prisma/client'],
     // Invoice uploads (phone photos/PDFs) and product photo uploads go through
     // server actions — the 1MB default rejects typical phone photos.
     serverActions: { bodySizeLimit: '10mb' },