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)

backend/knexfile.js

@@ -0,0 +1,46 @@
+require('dotenv').config();
+
+const path = require('path');
+
+// Database configuration for different environments
+const config = {
+  development: {
+    client: process.env.DATABASE_CLIENT || 'sqlite3',
+    connection: process.env.DATABASE_CLIENT === 'pg' ? {
+      host: process.env.DB_HOST || 'localhost',
+      port: process.env.DB_PORT || 5432,
+      user: process.env.DB_USER || 'postgres',
+      password: process.env.DB_PASSWORD || 'postgres',
+      database: process.env.DB_NAME || 'photo_sharing'
+    } : {
+      filename: path.join(__dirname, process.env.DATABASE_PATH || './data/photo_sharing.db')
+    },
+    useNullAsDefault: process.env.DATABASE_CLIENT !== 'pg',
+    migrations: {
+      directory: './migrations'
+    },
+    seeds: {
+      directory: './seeds'
+    }
+  },
+
+  production: {
+    client: process.env.DATABASE_CLIENT || 'pg',
+    connection: {
+      host: process.env.DB_HOST || 'postgres',
+      port: process.env.DB_PORT || 5432,
+      user: process.env.DB_USER || 'postgres',
+      password: process.env.DB_PASSWORD || 'postgres',
+      database: process.env.DB_NAME || 'photo_sharing'
+    },
+    pool: {
+      min: 2,
+      max: 10
+    },
+    migrations: {
+      directory: './migrations'
+    }
+  }
+};
+
+module.exports = config[process.env.NODE_ENV || 'development'];