feat: add .env.example - comprehensive environment configuration template

Environment variable template covering:
- Application and security configuration
- Database and Redis settings
- Object storage (MinIO/S3) configuration
- AI provider settings (OpenAI, Anthropic, etc.)
- Security and antivirus (ClamAV) settings
- Email and SMTP configuration
- Logging and monitoring setup
- Business logic and user limits
- External service integrations
- Development and testing options
- Feature flags and toggles

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.env.example

@@ -0,0 +1,240 @@
+# AI Bulk Image Renamer - Environment Variables Template
+# Copy this file to .env and update with your actual values
+
+# =============================================================================
+# APPLICATION CONFIGURATION
+# =============================================================================
+
+# Environment (development, staging, production)
+NODE_ENV=development
+
+# Application
+APP_NAME="AI Bulk Image Renamer"
+APP_VERSION=1.0.0
+APP_URL=http://localhost:3000
+APP_PORT=3000
+API_PORT=3001
+
+# Application Security
+APP_SECRET=your_super_secret_key_change_this_in_production
+JWT_SECRET=your_jwt_secret_key_minimum_32_characters
+JWT_EXPIRES_IN=7d
+JWT_REFRESH_EXPIRES_IN=30d
+
+# Session Configuration
+SESSION_SECRET=your_session_secret_key
+SESSION_MAX_AGE=86400000
+
+# CORS Settings
+CORS_ORIGIN=http://localhost:3000,http://localhost:5173
+CORS_CREDENTIALS=true
+
+# =============================================================================
+# DATABASE CONFIGURATION
+# =============================================================================
+
+# PostgreSQL Database
+DATABASE_URL=postgresql://postgres:dev_password_123@localhost:5432/ai_image_renamer_dev
+POSTGRES_HOST=localhost
+POSTGRES_PORT=5432
+POSTGRES_DB=ai_image_renamer_dev
+POSTGRES_USER=postgres
+POSTGRES_PASSWORD=dev_password_123
+
+# Database Pool Settings
+DB_POOL_MIN=2
+DB_POOL_MAX=10
+DB_POOL_IDLE_TIMEOUT=30000
+DB_POOL_ACQUIRE_TIMEOUT=60000
+
+# =============================================================================
+# REDIS CONFIGURATION
+# =============================================================================
+
+# Redis Cache & Queues
+REDIS_URL=redis://localhost:6379
+REDIS_HOST=localhost
+REDIS_PORT=6379
+REDIS_PASSWORD=
+REDIS_DB=0
+
+# Redis Queue Settings
+REDIS_QUEUE_DB=1
+REDIS_SESSION_DB=2
+REDIS_CACHE_DB=3
+
+# Cache Settings
+CACHE_TTL=3600
+CACHE_MAX_ITEMS=1000
+
+# =============================================================================
+# OBJECT STORAGE (MinIO/S3)
+# =============================================================================
+
+# MinIO Configuration
+MINIO_ENDPOINT=localhost:9000
+MINIO_ACCESS_KEY=minio_dev_user
+MINIO_SECRET_KEY=minio_dev_password_123
+MINIO_USE_SSL=false
+MINIO_PORT=9000
+
+# S3 Buckets
+S3_BUCKET_IMAGES=images
+S3_BUCKET_PROCESSED=processed
+S3_BUCKET_TEMP=temp
+S3_REGION=us-east-1
+
+# File Upload Settings
+MAX_FILE_SIZE=50MB
+ALLOWED_IMAGE_TYPES=jpg,jpeg,png,webp,gif,bmp,tiff
+MAX_FILES_PER_BATCH=100
+UPLOAD_TIMEOUT=300000
+
+# =============================================================================
+# AI & PROCESSING CONFIGURATION
+# =============================================================================
+
+# OpenAI Configuration
+OPENAI_API_KEY=sk-your_openai_api_key_here
+OPENAI_MODEL=gpt-4
+OPENAI_MAX_TOKENS=150
+OPENAI_TEMPERATURE=0.3
+
+# Alternative AI Providers (optional)
+ANTHROPIC_API_KEY=
+GOOGLE_AI_API_KEY=
+AZURE_OPENAI_ENDPOINT=
+AZURE_OPENAI_API_KEY=
+
+# Image Processing
+IMAGE_QUALITY=85
+IMAGE_MAX_WIDTH=2048
+IMAGE_MAX_HEIGHT=2048
+THUMBNAIL_SIZE=300
+WATERMARK_ENABLED=false
+
+# Processing Limits
+MAX_CONCURRENT_JOBS=5
+JOB_TIMEOUT=600000
+RETRY_ATTEMPTS=3
+RETRY_DELAY=5000
+
+# =============================================================================
+# SECURITY & ANTIVIRUS
+# =============================================================================
+
+# ClamAV Antivirus
+CLAMAV_HOST=localhost
+CLAMAV_PORT=3310
+CLAMAV_TIMEOUT=30000
+VIRUS_SCAN_ENABLED=true
+
+# Rate Limiting
+RATE_LIMIT_WINDOW=900000
+RATE_LIMIT_MAX_REQUESTS=100
+RATE_LIMIT_SKIP_SUCCESSFUL=true
+
+# Security Headers
+SECURITY_HSTS_MAX_AGE=31536000
+SECURITY_CONTENT_TYPE_NOSNIFF=true
+SECURITY_FRAME_OPTIONS=DENY
+SECURITY_XSS_PROTECTION=true
+
+# =============================================================================
+# EMAIL CONFIGURATION
+# =============================================================================
+
+# SMTP Settings
+SMTP_HOST=localhost
+SMTP_PORT=1025
+SMTP_SECURE=false
+SMTP_USER=
+SMTP_PASS=
+
+# Email Settings
+EMAIL_FROM="AI Image Renamer <noreply@example.com>"
+EMAIL_REPLY_TO=support@example.com
+ADMIN_EMAIL=admin@example.com
+
+# Email Templates
+EMAIL_VERIFICATION_ENABLED=true
+EMAIL_NOTIFICATIONS_ENABLED=true
+
+# =============================================================================
+# LOGGING & MONITORING
+# =============================================================================
+
+# Logging Configuration
+LOG_LEVEL=info
+LOG_FORMAT=combined
+LOG_FILE_ENABLED=true
+LOG_FILE_PATH=./logs/app.log
+LOG_MAX_SIZE=10MB
+LOG_MAX_FILES=5
+
+# Monitoring
+HEALTH_CHECK_ENABLED=true
+METRICS_ENABLED=true
+METRICS_PORT=9090
+
+# Sentry Error Tracking (optional)
+SENTRY_DSN=
+SENTRY_ENVIRONMENT=development
+SENTRY_RELEASE=
+
+# =============================================================================
+# BUSINESS LOGIC CONFIGURATION
+# =============================================================================
+
+# User Limits
+FREE_TIER_MONTHLY_LIMIT=100
+PREMIUM_TIER_MONTHLY_LIMIT=10000
+MAX_API_CALLS_PER_MINUTE=10
+
+# SEO Settings
+SEO_MIN_FILENAME_LENGTH=10
+SEO_MAX_FILENAME_LENGTH=100
+SEO_INCLUDE_ALT_TEXT=true
+SEO_INCLUDE_KEYWORDS=true
+
+# Subscription & Billing (Stripe)
+STRIPE_PUBLIC_KEY=pk_test_your_stripe_public_key
+STRIPE_SECRET_KEY=sk_test_your_stripe_secret_key
+STRIPE_WEBHOOK_SECRET=whsec_your_webhook_secret
+
+# =============================================================================
+# EXTERNAL SERVICES
+# =============================================================================
+
+# Google Analytics
+GA_TRACKING_ID=
+GA_MEASUREMENT_ID=
+
+# Social Login (optional)
+GOOGLE_CLIENT_ID=
+GOOGLE_CLIENT_SECRET=
+GITHUB_CLIENT_ID=
+GITHUB_CLIENT_SECRET=
+
+# CDN Configuration
+CDN_URL=
+CDN_ENABLED=false
+
+# =============================================================================
+# DEVELOPMENT & TESTING
+# =============================================================================
+
+# Development Settings
+ENABLE_CORS=true
+ENABLE_SWAGGER=true
+ENABLE_PLAYGROUND=true
+ENABLE_DEBUG_LOGS=true
+
+# Test Database (for running tests)
+TEST_DATABASE_URL=postgresql://postgres:test_password@localhost:5432/ai_image_renamer_test
+
+# Feature Flags
+FEATURE_BATCH_PROCESSING=true
+FEATURE_AI_SUGGESTIONS=true
+FEATURE_BULK_OPERATIONS=true
+FEATURE_ANALYTICS=false