feat: add format presets for common conversion scenarios

Format presets included:
**Video Presets:**
- YouTube Video (1080p, H.264, optimized)
- Instagram Video (Square format, 1:1)
- Twitter Video (720p, small file)
- Web Optimized (Streaming, low bitrate)

**Audio Presets:**
- Podcast (MP3, voice optimized, 128k)
- High Quality Music (MP3, 320k)
- Audiobook (Mono, 64k, small size)

**Image Presets:**
- Web Thumbnail (JPG, 800px width)
- HD Image (PNG, lossless, high quality)
- Social Media (JPG, 1200px, optimized)
- Web Optimized (WebP, small size)

Implementation:
- Created formatPresets.ts with 11 predefined presets
- FormatPresets component with responsive grid layout
- One-click preset application
- Automatically configures format and options
- Toast notification on preset selection
- Visual feedback with ring highlight
- Organized by category (video/audio/image)
- Emoji icons for visual appeal

User experience:
- Quick access to common conversion scenarios
- No need to manually configure complex settings
- Preset descriptions explain use case
- Disabled during active conversion
- Clear visual indication of selected preset

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

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

components/converter/FileConverter.tsx

@@ -9,6 +9,7 @@ import { FormatSelector } from './FormatSelector';
 import { ConversionPreview } from './ConversionPreview';
 import { ConversionOptionsPanel } from './ConversionOptions';
 import { FileInfo } from './FileInfo';
+import { FormatPresets } from './FormatPresets';
 import { useToast } from '@/components/ui/Toast';
 import {
   SUPPORTED_FORMATS,
@@ -20,6 +21,7 @@ import { convertWithFFmpeg } from '@/lib/converters/ffmpegService';
 import { convertWithImageMagick } from '@/lib/converters/imagemagickService';
 import { addToHistory } from '@/lib/storage/history';
 import { downloadBlobsAsZip, generateOutputFilename } from '@/lib/utils/fileUtils';
+import { getPresetById, type FormatPreset } from '@/lib/utils/formatPresets';
 import type { ConversionJob, ConversionFormat, ConversionOptions } from '@/types/conversion';
 
 export function FileConverter() {
@@ -209,6 +211,17 @@ export function FileConverter() {
     setSelectedFiles((prev) => prev.filter((_, i) => i !== index));
   };
 
+  const handlePresetSelect = (preset: FormatPreset) => {
+    // Find the output format that matches the preset
+    const format = compatibleFormats.find(f => f.extension === preset.outputFormat);
+
+    if (format) {
+      setOutputFormat(format);
+      setConversionOptions(preset.options);
+      addToast(`Applied ${preset.name} preset`, 'success');
+    }
+  };
+
   const handleDownloadAll = async () => {
     if (!outputFormat) return;
 
@@ -375,6 +388,15 @@ export function FileConverter() {
             <FileInfo file={selectedFiles[0]} format={inputFormat} />
           )}
 
+          {/* Format Presets */}
+          {inputFormat && (
+            <FormatPresets
+              inputFormat={inputFormat}
+              onPresetSelect={handlePresetSelect}
+              disabled={isConverting}
+            />
+          )}
+
           {/* Format selection */}
           {inputFormat && compatibleFormats.length > 0 && (
             <div className="grid grid-cols-1 md:grid-cols-[1fr_auto_1fr] gap-4 items-start">