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">

components/converter/FormatPresets.tsx

@@ -0,0 +1,67 @@
+'use client';
+
+import * as React from 'react';
+import { Sparkles } from 'lucide-react';
+import { Card } from '@/components/ui/Card';
+import { Button } from '@/components/ui/Button';
+import { cn } from '@/lib/utils/cn';
+import { getPresetsByCategory, type FormatPreset } from '@/lib/utils/formatPresets';
+import type { ConversionFormat } from '@/types/conversion';
+
+interface FormatPresetsProps {
+  inputFormat: ConversionFormat;
+  onPresetSelect: (preset: FormatPreset) => void;
+  disabled?: boolean;
+}
+
+export function FormatPresets({ inputFormat, onPresetSelect, disabled = false }: FormatPresetsProps) {
+  const [selectedPresetId, setSelectedPresetId] = React.useState<string | null>(null);
+
+  // Get presets for the input format's category
+  const presets = getPresetsByCategory(inputFormat.category);
+
+  if (presets.length === 0) {
+    return null;
+  }
+
+  const handlePresetClick = (preset: FormatPreset) => {
+    setSelectedPresetId(preset.id);
+    onPresetSelect(preset);
+  };
+
+  return (
+    <Card className="p-4">
+      <div className="flex items-center gap-2 mb-4">
+        <Sparkles className="h-5 w-5 text-primary" />
+        <h3 className="text-sm font-semibold">Quick Presets</h3>
+      </div>
+
+      <div className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-3">
+        {presets.map((preset) => (
+          <Button
+            key={preset.id}
+            onClick={() => handlePresetClick(preset)}
+            variant={selectedPresetId === preset.id ? 'default' : 'outline'}
+            className={cn(
+              'h-auto py-4 px-4 flex flex-col items-start text-left gap-2',
+              selectedPresetId === preset.id && 'ring-2 ring-primary ring-offset-2'
+            )}
+            disabled={disabled}
+          >
+            <div className="flex items-center gap-2 w-full">
+              <span className="text-2xl">{preset.icon}</span>
+              <div className="flex-1 min-w-0">
+                <div className="font-semibold text-sm">{preset.name}</div>
+              </div>
+            </div>
+            <p className="text-xs text-muted-foreground w-full">{preset.description}</p>
+          </Button>
+        ))}
+      </div>
+
+      <div className="mt-3 text-xs text-muted-foreground">
+        Select a preset to automatically configure optimal settings for your use case
+      </div>
+    </Card>
+  );
+}