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>

lib/wasm/wasmLoader.ts

@@ -7,7 +7,6 @@ import type { ConverterEngine, WASMModuleState } from '@/types/conversion';
 const moduleState: WASMModuleState = {
   ffmpeg: false,
   imagemagick: false,
-  pandoc: false,
 };
 
 /**
@@ -15,7 +14,6 @@ const moduleState: WASMModuleState = {
  */
 let ffmpegInstance: FFmpeg | null = null;
 let imagemagickInstance: any = null;
-let pandocInstance: any = null;
 
 /**
  * Load FFmpeg WASM module
@@ -75,33 +73,6 @@ export async function loadImageMagick(): Promise<any> {
   }
 }
 
-/**
- * Load Pandoc converter (uses pure JavaScript libraries, not WASM)
- * Note: We use marked + turndown instead of actual Pandoc WASM
- */
-export async function loadPandoc(): Promise<any> {
-  if (pandocInstance && moduleState.pandoc) {
-    return pandocInstance;
-  }
-
-  try {
-    // Import the converter libraries
-    const [marked, turndown] = await Promise.all([
-      import('marked'),
-      import('turndown'),
-    ]);
-
-    pandocInstance = { marked, turndown };
-    moduleState.pandoc = true;
-    console.log('Document converter loaded successfully');
-
-    return pandocInstance;
-  } catch (error) {
-    console.error('Failed to load document converter:', error);
-    throw new Error('Failed to load document converter');
-  }
-}
-
 /**
  * Get loaded module state
  */
@@ -125,8 +96,6 @@ export async function loadModule(engine: ConverterEngine): Promise<any> {
       return loadFFmpeg();
     case 'imagemagick':
       return loadImageMagick();
-    case 'pandoc':
-      return loadPandoc();
     default:
       throw new Error(`Unknown converter engine: ${engine}`);
   }
@@ -148,10 +117,5 @@ export function unloadAll(): void {
     moduleState.imagemagick = false;
   }
 
-  if (pandocInstance) {
-    pandocInstance = null;
-    moduleState.pandoc = false;
-  }
-
   console.log('All WASM modules unloaded');
 }