feat: Add PostgreSQL database infrastructure

- Add SQLAlchemy models for User, Translation, ApiKey, UsageLog, PaymentHistory
- Add database connection management with PostgreSQL/SQLite support
- Add repository layer for CRUD operations
- Add Alembic migration setup with initial migration
- Update auth_service to automatically use database when DATABASE_URL is set
- Update docker-compose.yml with PostgreSQL service and Redis (non-optional)
- Add database migration script (scripts/migrate_to_db.py)
- Update .env.example with database configuration

scripts/migrate_to_db.py

@@ -0,0 +1,160 @@
+"""
+Migration script to move data from JSON files to database
+Run this once to migrate existing users to the new database system
+"""
+import json
+import os
+import sys
+from pathlib import Path
+from datetime import datetime
+
+# Add parent directory to path
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from database.connection import init_db, get_db_session
+from database.repositories import UserRepository
+from database.models import PlanType, SubscriptionStatus
+
+
+def migrate_users_from_json():
+    """Migrate users from JSON file to database"""
+    json_path = Path("data/users.json")
+    
+    if not json_path.exists():
+        print("No users.json found, nothing to migrate")
+        return 0
+    
+    # Initialize database
+    print("Initializing database tables...")
+    init_db()
+    
+    # Load JSON data
+    with open(json_path, 'r') as f:
+        users_data = json.load(f)
+    
+    print(f"Found {len(users_data)} users to migrate")
+    
+    migrated = 0
+    skipped = 0
+    errors = 0
+    
+    with get_db_session() as db:
+        repo = UserRepository(db)
+        
+        for user_id, user_data in users_data.items():
+            try:
+                # Check if user already exists
+                existing = repo.get_by_email(user_data.get('email', ''))
+                if existing:
+                    print(f"  Skipping {user_data.get('email')} - already exists")
+                    skipped += 1
+                    continue
+                
+                # Map plan string to enum
+                plan_str = user_data.get('plan', 'free')
+                try:
+                    plan = PlanType(plan_str)
+                except ValueError:
+                    plan = PlanType.FREE
+                
+                # Map subscription status
+                status_str = user_data.get('subscription_status', 'active')
+                try:
+                    status = SubscriptionStatus(status_str)
+                except ValueError:
+                    status = SubscriptionStatus.ACTIVE
+                
+                # Create user with original ID
+                from database.models import User
+                user = User(
+                    id=user_id,
+                    email=user_data.get('email', '').lower(),
+                    name=user_data.get('name', ''),
+                    password_hash=user_data.get('password_hash', ''),
+                    email_verified=user_data.get('email_verified', False),
+                    avatar_url=user_data.get('avatar_url'),
+                    plan=plan,
+                    subscription_status=status,
+                    stripe_customer_id=user_data.get('stripe_customer_id'),
+                    stripe_subscription_id=user_data.get('stripe_subscription_id'),
+                    docs_translated_this_month=user_data.get('docs_translated_this_month', 0),
+                    pages_translated_this_month=user_data.get('pages_translated_this_month', 0),
+                    api_calls_this_month=user_data.get('api_calls_this_month', 0),
+                    extra_credits=user_data.get('extra_credits', 0),
+                )
+                
+                # Parse dates
+                if user_data.get('created_at'):
+                    try:
+                        user.created_at = datetime.fromisoformat(user_data['created_at'].replace('Z', '+00:00'))
+                    except:
+                        pass
+                
+                if user_data.get('updated_at'):
+                    try:
+                        user.updated_at = datetime.fromisoformat(user_data['updated_at'].replace('Z', '+00:00'))
+                    except:
+                        pass
+                
+                db.add(user)
+                db.commit()
+                
+                print(f"  Migrated: {user.email}")
+                migrated += 1
+                
+            except Exception as e:
+                print(f"  Error migrating {user_data.get('email', user_id)}: {e}")
+                errors += 1
+                db.rollback()
+    
+    print(f"\nMigration complete:")
+    print(f"  Migrated: {migrated}")
+    print(f"  Skipped: {skipped}")
+    print(f"  Errors: {errors}")
+    
+    # Backup original file
+    if migrated > 0:
+        backup_path = json_path.with_suffix('.json.bak')
+        os.rename(json_path, backup_path)
+        print(f"\nOriginal file backed up to: {backup_path}")
+    
+    return migrated
+
+
+def verify_migration():
+    """Verify the migration was successful"""
+    from database.connection import get_db_session
+    from database.repositories import UserRepository
+    
+    with get_db_session() as db:
+        repo = UserRepository(db)
+        count = repo.count_users()
+        print(f"\nDatabase now contains {count} users")
+        
+        # List first 5 users
+        users = repo.get_all_users(limit=5)
+        if users:
+            print("\nSample users:")
+            for user in users:
+                print(f"  - {user.email} ({user.plan.value})")
+
+
+if __name__ == "__main__":
+    print("=" * 50)
+    print("JSON to Database Migration Script")
+    print("=" * 50)
+    
+    # Check environment
+    db_url = os.getenv("DATABASE_URL", "")
+    if db_url:
+        print(f"Database: PostgreSQL")
+    else:
+        print(f"Database: SQLite (development)")
+    
+    print()
+    
+    # Run migration
+    migrate_users_from_json()
+    
+    # Verify
+    verify_migration()