Add voice input UI components for hands-free tracking

Implemented complete voice input user interface:

**Voice Recording Hook (useVoiceInput):**
- Browser Web Speech API integration
- Real-time speech recognition
- Continuous and interim results
- 10-second auto-timeout
- Error handling for permissions, network, audio issues
- Graceful fallback for unsupported browsers

**Voice Input Button Component:**
- Modal dialog with microphone button
- Animated pulsing microphone when recording
- Real-time transcript display
- Automatic intent classification on completion
- Structured data visualization
- Example commands for user guidance
- Success/error feedback with MUI Alerts
- Confidence level indicators

**Floating Action Button:**
- Always-visible FAB in bottom-right corner
- Quick access from any page
- Auto-navigation to appropriate tracking page
- Snackbar feedback messages
- Mobile-optimized positioning (thumb zone)

**Integration with Tracking Pages:**
- Voice button in feeding page header
- Auto-fills form fields from voice commands
- Seamless voice-to-form workflow
- Example: "Fed baby 120ml" → fills bottle type & amount

**Features:**
- ✅ Browser speech recognition (Chrome, Edge, Safari)
- ✅ Real-time transcription display
- ✅ Automatic intent classification
- ✅ Auto-fill tracking forms
- ✅ Visual feedback (animations, colors)
- ✅ Error handling & user guidance
- ✅ Mobile-optimized design
- ✅ Accessibility support

**User Flow:**
1. Click microphone button (floating or in-page)
2. Speak command: "Fed baby 120 ml"
3. See real-time transcript
4. Auto-classification shows intent & data
5. Click "Use Command"
6. Form auto-fills or activity created

**Browser Support:**
- Chrome ✅
- Edge ✅
- Safari ✅
- Firefox ❌ (Web Speech API not supported)

**Files Created:**
- hooks/useVoiceInput.ts - Speech recognition hook
- components/voice/VoiceInputButton.tsx - Modal input component
- components/voice/VoiceFloatingButton.tsx - FAB for quick access
- app/layout.tsx - Added floating button globally
- app/track/feeding/page.tsx - Added voice button to header

Voice input is now accessible from anywhere in the app, providing
true hands-free tracking for parents.

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

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

maternal-web/app/layout.tsx

@@ -3,6 +3,7 @@ import { Inter } from 'next/font/google';
 import { ThemeRegistry } from '@/components/ThemeRegistry';
 import { ErrorBoundary } from '@/components/common/ErrorBoundary';
 import { ReduxProvider } from '@/components/providers/ReduxProvider';
+import { VoiceFloatingButton } from '@/components/voice/VoiceFloatingButton';
 // import { PerformanceMonitor } from '@/components/common/PerformanceMonitor'; // Temporarily disabled
 import './globals.css';
 
@@ -44,6 +45,7 @@ export default function RootLayout({
             <ThemeRegistry>
               {/* <PerformanceMonitor /> */}
               {children}
+              <VoiceFloatingButton />
             </ThemeRegistry>
           </ReduxProvider>
         </ErrorBoundary>