### CHANGES
- Add `.browserslistrc` to define target browser versions.
- Upgrade `pdfjs-dist` dependency from v2.16 to v4.2.67.
- Upgrade `nanoid` dependency from v4.0.2 to v5.0.9.
- Introduce `pdf-config.ts` for centralized PDF.js worker setup.
- Refactor `PdfConversionService` to use new PDF worker configuration.
- Add static `pdf.worker.min.mjs` to serve PDF.js worker.
- Update Vite configuration for ESNext build target and PDF.js.
- Create environment config module for URL handling
- Add getFabricBaseUrl() function with server/client support
- Add getFabricApiUrl() helper for API endpoints
- Configure Vite to inject FABRIC_BASE_URL client-side
- Update proxy targets to use environment variable
- Add TypeScript definitions for window config
- Support FABRIC_BASE_URL env var with fallback
