Add voice intent classification for hands-free tracking

Implemented comprehensive voice command understanding system:

**Intent Classification:**
- Feeding intent (bottle, breastfeeding, solid food)
- Sleep intent (naps, nighttime sleep)
- Diaper intent (wet, dirty, both, dry)
- Unknown intent handling

**Entity Extraction:**
- Amounts with units (ml, oz, tbsp): "120 ml", "4 ounces"
- Durations in minutes: "15 minutes", "for 20 mins"
- Time expressions: "at 3:30 pm", "30 minutes ago", "just now"
- Breast feeding side: "left", "right", "both"
- Diaper types: "wet", "dirty", "both"
- Sleep types: "nap", "night"

**Structured Data Output:**
- FeedingData: type, amount, unit, duration, side, timestamps
- SleepData: type, duration, start/end times
- DiaperData: type, timestamp
- Ready for direct activity creation

**Pattern Matching:**
- 15+ feeding patterns (bottle, breast, solid)
- 8+ sleep patterns (nap, sleep, woke up)
- 8+ diaper patterns (wet, dirty, bowel movement)
- Robust keyword detection with variations

**Confidence Scoring:**
- High: >= 0.8 (strong match)
- Medium: 0.5-0.79 (probable match)
- Low: < 0.5 (uncertain)
- Minimum threshold: 0.3 for validation

**API Endpoint:**
- POST /api/voice/transcribe - Classify text or audio
- GET /api/voice/transcribe - Get supported commands
- JSON response with intent, confidence, entities, structured data
- Audio transcription placeholder (Whisper integration ready)

**Implementation Files:**
- lib/voice/intentClassifier.ts - Core classification (600+ lines)
- app/api/voice/transcribe/route.ts - API endpoint
- scripts/test-voice-intent.mjs - Test suite (25 tests)
- lib/voice/README.md - Complete documentation

**Test Coverage:** 25 tests, 100% pass rate
✅ Bottle feeding (3 tests)
✅ Breastfeeding (3 tests)
✅ Solid food (2 tests)
✅ Sleep tracking (6 tests)
✅ Diaper changes (7 tests)
✅ Edge cases (4 tests)

**Example Commands:**
- "Fed baby 120 ml" → bottle, 120ml
- "Nursed on left breast for 15 minutes" → breast_left, 15min
- "Changed wet and dirty diaper" → both
- "Napped for 45 minutes" → nap, 45min

System converts natural language to structured tracking data with
high accuracy for common parenting voice commands.

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

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

maternal-web/app/api/voice/transcribe/route.ts

@@ -0,0 +1,139 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { classifyIntent, validateClassification, getConfidenceLevel } from '@/lib/voice/intentClassifier';
+
+/**
+ * Voice transcription and intent classification endpoint
+ *
+ * Accepts audio file or transcribed text and returns:
+ * - Intent classification (feeding/sleep/diaper)
+ * - Extracted entities (amounts, times, durations)
+ * - Structured data ready for activity creation
+ */
+export async function POST(request: NextRequest) {
+  try {
+    const contentType = request.headers.get('content-type') || '';
+
+    let transcribedText: string;
+
+    if (contentType.includes('application/json')) {
+      // Text input (already transcribed)
+      const body = await request.json();
+      transcribedText = body.text;
+
+      if (!transcribedText || typeof transcribedText !== 'string') {
+        return NextResponse.json(
+          {
+            error: 'VOICE_INVALID_INPUT',
+            message: 'Text must be a non-empty string',
+          },
+          { status: 400 }
+        );
+      }
+    } else if (contentType.includes('multipart/form-data')) {
+      // Audio file upload (needs transcription)
+      // TODO: Implement Whisper API integration for audio transcription
+      // For now, return not implemented
+      return NextResponse.json(
+        {
+          error: 'VOICE_AUDIO_NOT_IMPLEMENTED',
+          message: 'Audio transcription not yet implemented. Use text input for now.',
+          hint: 'Send JSON with { "text": "your voice command" }',
+        },
+        { status: 501 }
+      );
+    } else {
+      return NextResponse.json(
+        {
+          error: 'VOICE_INVALID_CONTENT_TYPE',
+          message: 'Content-Type must be application/json or multipart/form-data',
+        },
+        { status: 400 }
+      );
+    }
+
+    // Classify intent
+    const classification = classifyIntent(transcribedText);
+
+    // Validate classification
+    if (!validateClassification(classification)) {
+      return NextResponse.json(
+        {
+          error: 'VOICE_CLASSIFICATION_FAILED',
+          message: 'Could not understand the command. Please try again.',
+          suggestion: 'Try saying something like "Fed baby 100ml" or "Changed wet diaper"',
+          classification: {
+            intent: classification.intent,
+            confidence: classification.confidence,
+            confidenceLevel: getConfidenceLevel(classification.confidence),
+          },
+        },
+        { status: 400 }
+      );
+    }
+
+    // Return classification result
+    return NextResponse.json(
+      {
+        success: true,
+        transcription: transcribedText,
+        classification: {
+          intent: classification.intent,
+          confidence: classification.confidence,
+          confidenceLevel: getConfidenceLevel(classification.confidence),
+          entities: classification.entities,
+          structuredData: classification.structuredData,
+        },
+      },
+      { status: 200 }
+    );
+  } catch (error) {
+    console.error('[Voice] Transcription error:', error);
+    return NextResponse.json(
+      {
+        error: 'VOICE_TRANSCRIPTION_FAILED',
+        message: 'Failed to process voice command. Please try again.',
+      },
+      { status: 500 }
+    );
+  }
+}
+
+/**
+ * Get supported voice commands and examples
+ */
+export async function GET() {
+  return NextResponse.json(
+    {
+      supportedIntents: ['feeding', 'sleep', 'diaper'],
+      examples: {
+        feeding: [
+          'Fed baby 120 ml',
+          'Gave him 4 ounces',
+          'Nursed on left breast for 15 minutes',
+          'Breastfed on both sides',
+          'Baby ate solid food',
+        ],
+        sleep: [
+          'Baby fell asleep',
+          'Napped for 45 minutes',
+          'Put baby down for bedtime',
+          'Baby woke up',
+        ],
+        diaper: [
+          'Changed wet diaper',
+          'Dirty diaper change',
+          'Changed a wet and dirty diaper',
+          'Baby had a bowel movement',
+        ],
+      },
+      entities: {
+        amounts: ['120 ml', '4 oz', '2 tablespoons'],
+        durations: ['15 minutes', '45 mins', '2 hours'],
+        times: ['at 3:30 pm', '30 minutes ago', 'just now'],
+        breastSides: ['left breast', 'right side', 'both sides'],
+        diaperTypes: ['wet', 'dirty', 'wet and dirty', 'bowel movement'],
+      },
+    },
+    { status: 200 }
+  );
+}