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/alembic/env.py

@@ -0,0 +1,52 @@
+from logging.config import fileConfig
+from sqlalchemy import engine_from_config, pool
+from alembic import context
+import sys
+import os
+
+# Add the backend directory to the path
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from app.models.base import Base
+from app.models import Category, Question, GameSession, GameEvent, Admin
+
+config = context.config
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+target_metadata = Base.metadata
+
+
+def run_migrations_offline() -> None:
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()