fix: configure PostgreSQL for production and clean up deployment

- Fix database configuration to use PostgreSQL in production
- Add knexfile.js to support both SQLite (dev) and PostgreSQL (prod)
- Create admin user creation script (scripts/create-admin.js)
- Clean up docker-compose files:
  - Remove redundant docker-compose.yml and docker-compose.local.yml
  - Create docker-compose.dev.yml for development
  - Update docker-compose.prod.yml with proper DB configuration
- Clean up environment files:
  - Update .env.example for development
  - Update .env.production.example with proper settings
  - Remove redundant .env.local
- Update backend .env.example with database configuration options
- Create comprehensive DEPLOYMENT.md with admin setup instructions
- Fix production database name consistency (picpeak instead of photoapp)

.env.example

@@ -1,26 +1,34 @@
-# JWT Secret for authentication
-# IMPORTANT: Generate a secure random secret with: openssl rand -hex 32
-# NEVER use the default value or commit the actual secret to version control
-JWT_SECRET=CHANGE_ME_TO_A_64_CHARACTER_SECURE_RANDOM_STRING_GENERATED_BY_OPENSSL
+# Environment Configuration Template
+# Copy this file to .env and adjust values for your environment
 
-# URLs
-ADMIN_URL=https://admin.photos.yourdomain.com
-FRONTEND_URL=https://photos.yourdomain.com
+# Development: Use docker-compose.dev.yml
+# Production: Use docker-compose.prod.yml with .env.production.example
 
-# Database (for PostgreSQL in production)
-DB_USER=photoapp
-DB_PASSWORD=secure-password-here
-DB_NAME=photo_sharing
+# JWT Secret (CRITICAL for production)
+# Generate with: openssl rand -base64 32
+JWT_SECRET=dev-secret-change-in-production
+
+# Application URLs
+ADMIN_URL=http://localhost:3005
+FRONTEND_URL=http://localhost:3005
+
+# Database Configuration
+# SQLite is used for development by default
+# For production PostgreSQL config, see .env.production.example
+DATABASE_CLIENT=sqlite3
+DATABASE_PATH=./data/photo_sharing.db
 
 # Email Configuration
-SMTP_HOST=smtp.gmail.com
-SMTP_PORT=587
+# Development: Uses Mailhog (included in docker-compose.dev.yml)
+# Production: Configure real SMTP server
+SMTP_HOST=mailhog
+SMTP_PORT=1025
 SMTP_SECURE=false
-SMTP_USER=your-email@gmail.com
-SMTP_PASS=your-app-password
-EMAIL_FROM=noreply@yourdomain.com
+SMTP_USER=
+SMTP_PASS=
+EMAIL_FROM=noreply@localhost
 
-# Umami Analytics
-UMAMI_URL=https://analytics.yourdomain.com
-UMAMI_WEBSITE_ID=your-website-id
-UMAMI_HASH_SALT=random-salt-here
+# Optional: Umami Analytics
+UMAMI_URL=
+UMAMI_WEBSITE_ID=
+UMAMI_HASH_SALT=