chore: consolidate env templates and remove Docker docs from master

- Merge .env.production.template into .env.example
- Remove Docker Deployment section from CLAUDE.md (now on docker branch)
- Update README.md to reference .env.example
- Update environment variable documentation

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

.env.example

@@ -1,22 +1,47 @@
 # Application Configuration
 # Copy this file to .env and update with your values
 
-# Hostname for the application (e.g., https://awards.dj7nt.de)
+# ===================================================================
+# Environment
+# ===================================================================
+# Development: development
+# Production: production
+NODE_ENV=development
+
+# Log Level (debug, info, warn, error)
+# Development: debug
+# Production: info
+LOG_LEVEL=debug
+
+# Server Port (default: 3001)
+PORT=3001
+
+# ===================================================================
+# URLs
+# ===================================================================
+# Frontend URL (e.g., https://awards.dj7nt.de)
 # Leave empty for development (uses localhost)
 VITE_APP_URL=
 
-# API Base URL (in production, can be same domain or separate)
-# Leave empty to use relative paths (recommended for same-domain deployment)
+# API Base URL (leave empty for same-domain deployment)
+# Only set if API is on different domain
 VITE_API_BASE_URL=
 
 # Allowed CORS origins for backend (comma-separated)
-# Only needed for production if not using same domain
+# Add all domains that should access the API
 # Example: https://awards.dj7nt.de,https://www.awards.dj7nt.de
 ALLOWED_ORIGINS=
 
-# JWT Secret (for production, use a strong random string)
-# Generate with: openssl rand -base64 32
+# ===================================================================
+# Security
+# ===================================================================
+# JWT Secret (REQUIRED for production)
+# Development: uses default if not set
+# Production: Generate with: openssl rand -base64 32
 JWT_SECRET=change-this-in-production
 
-# Node Environment
-NODE_ENV=development
+# ===================================================================
+# Database (Optional)
+# ===================================================================
+# Leave empty to use default SQLite database
+# DATABASE_URL=file:/path/to/custom.db