feat(phase1): Complete development environment configuration

- Configure Alembic for database migrations with initial schema
- Fix base.py to use lazy loading for async engine (avoids import-time issues)
- Change AI model from sonnet to haiku (claude-3-haiku-20240307)
- Fix pytest version compatibility with pytest-asyncio
- Add frontend package-lock.json

Phase 1 tasks completed:
- F1.1: Development environment (Docker, Node.js 20, Python 3.12, venv)
- F1.2: PostgreSQL with 8 categories seeded
- F1.3: Redis connection verified
- F1.4: Anthropic API configured and tested
- F1.5: Backend server + WebSocket verified

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/services/ai_generator.py

@@ -63,7 +63,7 @@ Responde SOLO con el JSON, sin texto adicional."""
 
         try:
             message = self.client.messages.create(
-                model="claude-3-5-sonnet-20241022",
+                model="claude-3-haiku-20240307",
                 max_tokens=2000,
                 messages=[
                     {"role": "user", "content": prompt}