refactor: remove all document conversion support, keep only media conversions

This commit completely removes document conversion functionality to focus
exclusively on media file conversions (video, audio, images).

Changes:
- Remove all document converter services (pandocService.ts, pdfService.ts, docxService.ts)
- Uninstall document-related packages: marked, turndown, dompurify, jspdf, pdfjs-dist, docx, mammoth, @types/turndown
- Remove document formats (PDF, DOCX, Markdown, HTML, TXT) from formatMappings.ts
- Remove pandoc converter from FileConverter.tsx
- Remove pandoc loader and references from wasmLoader.ts
- Update TypeScript types to remove 'pandoc' from ConverterEngine and 'document' from FileCategory
- Remove pandoc from WASMModuleState interface
- Update README.md to remove all document conversion documentation
- Update UI descriptions to reflect media-only conversions

Supported conversions now:
- Video: MP4, WebM, AVI, MOV, MKV, GIF
- Audio: MP3, WAV, OGG, AAC, FLAC
- Images: PNG, JPG, WebP, GIF, BMP, TIFF, SVG

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

components/converter/FileConverter.tsx

@@ -16,7 +16,6 @@ import {
 } from '@/lib/utils/formatMappings';
 import { convertWithFFmpeg } from '@/lib/converters/ffmpegService';
 import { convertWithImageMagick } from '@/lib/converters/imagemagickService';
-import { convertWithPandoc } from '@/lib/converters/pandocService';
 import { addToHistory } from '@/lib/storage/history';
 import type { ConversionJob, ConversionFormat } from '@/types/conversion';
 
@@ -111,12 +110,6 @@ export function FileConverter() {
           );
           break;
 
-        case 'pandoc':
-          result = await convertWithPandoc(selectedFile, outputFormat.extension, {}, (progress) => {
-            setConversionJob((prev) => prev && { ...prev, progress });
-          });
-          break;
-
         default:
           throw new Error(`Unknown converter: ${outputFormat.converter}`);
       }
@@ -184,7 +177,7 @@ export function FileConverter() {
         <CardHeader>
           <CardTitle>File Converter</CardTitle>
           <CardDescription>
-            Convert videos, images, and documents directly in your browser using WebAssembly
+            Convert videos, audio, and images directly in your browser using WebAssembly
           </CardDescription>
         </CardHeader>
         <CardContent className="space-y-6">