- Fix file viewer not sending JWT auth tokens when loading files
- inlineViewer.js: already used XHR with auth (images/PDFs worked)
- fileViewer.js: was setting img.src/iframe.src directly without auth headers,
now uses fetch with Bearer token and blob URLs
- ui.js/contextMenus.js/fileRenderer.js/recent.js/favorites.js: replaced all
window.location.href = /api/files/... (unauthenticated navigation) with
authenticated viewer or fileOps.downloadFile()
- Add text file viewing support (text/*, application/json, etc.)
- New createTextViewer() in inlineViewer.js with authenticated fetch
- New loadTextViewer() in fileViewer.js with authenticated fetch
- New isViewableFile() helper in ui.js used across all entry points
- CSS styles for .inline-viewer-text-content and .file-viewer-text-content
- Translate remaining Spanish strings to English in viewer files
Fixes: text files showing 'Token not provided', images failing to load,
and text files not being previewable at all.