feat: create comprehensive .env.example configuration template

- Add 70+ environment variables organized in logical sections
- Include app metadata, server settings, security, and performance options
- Add feature flags, monitoring, and asset optimization settings
- Provide production-safe defaults with development overrides
- Document all configuration options with clear section headers
- Support file upload limits, CORS configuration, and template settings

.env.example

@@ -0,0 +1,275 @@
+# UnitForge Environment Configuration
+# Copy this file to .env and modify the values as needed
+
+# =============================================================================
+# APPLICATION INFORMATION
+# =============================================================================
+
+APP_NAME=UnitForge
+APP_VERSION=1.0.0
+APP_DESCRIPTION="Create, validate, and manage systemd unit files"
+
+# =============================================================================
+# EXTERNAL LINKS
+# =============================================================================
+
+GITHUB_URL=https://github.com/will666/unitforge
+DOCUMENTATION_URL=https://unitforge.readthedocs.io/
+BUG_REPORTS_URL=https://github.com/will666/unitforge/issues
+
+# =============================================================================
+# CONTACT INFORMATION
+# =============================================================================
+
+CONTACT_EMAIL=contact@unitforge.dev
+
+# =============================================================================
+# APPLICATION SETTINGS
+# =============================================================================
+
+DEBUG=false
+ENVIRONMENT=production
+LOG_LEVEL=info
+
+# =============================================================================
+# SERVER CONFIGURATION
+# =============================================================================
+
+HOST=0.0.0.0
+PORT=8000
+RELOAD=false
+WORKERS=4
+
+# =============================================================================
+# API CONFIGURATION
+# =============================================================================
+
+API_TITLE="${APP_NAME}"
+API_VERSION="${APP_VERSION}"
+API_DESCRIPTION=${APP_DESCRIPTION}
+DOCS_URL="/api/docs"
+REDOC_URL="/api/redoc"
+
+# =============================================================================
+# SECURITY SETTINGS
+# =============================================================================
+
+# IMPORTANT: Generate a secure secret key for production
+SECRET_KEY=your-secret-key-here
+ALLOWED_HOSTS=["*"]
+
+# =============================================================================
+# CORS CONFIGURATION
+# =============================================================================
+
+# Use "*" for all origins or comma-separated list of allowed origins
+# Examples:
+# CORS_ORIGINS=*
+# CORS_ORIGINS=["https://yourdomain.com", "https://www.yourdomain.com"]
+CORS_ORIGINS=*
+
+# =============================================================================
+# DATABASE (Future Use)
+# =============================================================================
+
+# DATABASE_URL="sqlite:///./unitforge.db"
+
+# =============================================================================
+# FILE UPLOAD SETTINGS
+# =============================================================================
+
+# Maximum file upload size in bytes (1MB)
+MAX_UPLOAD_SIZE=1048576
+ALLOWED_EXTENSIONS=[".service", ".timer", ".socket", ".mount", ".target", ".path"]
+
+# =============================================================================
+# TEMPLATE SETTINGS
+# =============================================================================
+
+# Template cache time-to-live in seconds (5 minutes)
+TEMPLATE_CACHE_TTL=300
+# Validation cache time-to-live in seconds (1 minute)
+VALIDATION_CACHE_TTL=60
+
+# =============================================================================
+# DEVELOPMENT TOOLS (Override for Development)
+# =============================================================================
+
+# Test options (development only)
+# PYTEST_ADDOPTS="-v --tb=short --strict-markers"
+# COVERAGE_REPORT_DIR="htmlcov"
+# MYPY_CONFIG_FILE="pyproject.toml"
+
+# =============================================================================
+# UV PACKAGE MANAGER SETTINGS
+# =============================================================================
+
+# UV package manager cache directory
+# UV_CACHE_DIR=".uv-cache"
+# UV_PYTHON="python3"
+
+# =============================================================================
+# DOCKER SETTINGS
+# =============================================================================
+
+# Docker build settings
+# DOCKER_BUILDKIT=1
+# COMPOSE_DOCKER_CLI_BUILD=1
+
+# =============================================================================
+# PATHS
+# =============================================================================
+
+FRONTEND_DIR="frontend"
+BACKEND_DIR="backend"
+STATIC_DIR="frontend/static"
+TEMPLATES_DIR="frontend/templates"
+
+# =============================================================================
+# FEATURE FLAGS
+# =============================================================================
+
+ENABLE_API_METRICS=false
+ENABLE_REQUEST_LOGGING=true
+ENABLE_TEMPLATE_CACHING=true
+ENABLE_VALIDATION_CACHING=true
+
+# =============================================================================
+# PERFORMANCE SETTINGS
+# =============================================================================
+
+REQUEST_TIMEOUT=30
+KEEPALIVE_TIMEOUT=5
+MAX_CONNECTIONS=100
+
+# =============================================================================
+# LOGGING CONFIGURATION
+# =============================================================================
+
+LOG_FORMAT="%(asctime)s - %(name)s - %(levelname)s - %(message)s"
+LOG_DATE_FORMAT="%Y-%m-%d %H:%M:%S"
+ACCESS_LOG=true
+
+# =============================================================================
+# DEVELOPMENT SERVER OPTIONS (Development Only)
+# =============================================================================
+
+# Development server auto-reload settings
+# AUTO_RELOAD=false
+# RELOAD_DIRS=["backend", "frontend"]
+# RELOAD_DELAY=0.25
+
+# =============================================================================
+# TESTING CONFIGURATION
+# =============================================================================
+
+# Testing configuration
+# TEST_DATABASE_URL="sqlite:///:memory:"
+# TEST_PARALLEL=true
+# TEST_COVERAGE_THRESHOLD=80
+
+# =============================================================================
+# CLI CONFIGURATION
+# =============================================================================
+
+CLI_VERBOSE=false
+CLI_COLOR=true
+CLI_PROGRESS=true
+
+# =============================================================================
+# VALIDATION SETTINGS
+# =============================================================================
+
+STRICT_VALIDATION=false
+SHOW_WARNINGS=true
+MAX_VALIDATION_ERRORS=50
+
+# =============================================================================
+# TEMPLATE GENERATION DEFAULTS
+# =============================================================================
+
+DEFAULT_USER="www-data"
+DEFAULT_GROUP="www-data"
+DEFAULT_RESTART_POLICY="on-failure"
+DEFAULT_WANTED_BY="multi-user.target"
+
+# =============================================================================
+# SECURITY HEADERS
+# =============================================================================
+
+SECURITY_HEADERS=true
+# HSTS max age in seconds (1 year)
+HSTS_MAX_AGE=31536000
+CSP_ENABLED=true
+
+# =============================================================================
+# MONITORING
+# =============================================================================
+
+HEALTH_CHECK_ENABLED=true
+METRICS_ENABLED=false
+TRACING_ENABLED=false
+
+# =============================================================================
+# ASSET OPTIMIZATION
+# =============================================================================
+
+HOT_RELOAD=false
+SOURCE_MAPS=false
+MINIFY_ASSETS=true
+COMPRESS_RESPONSES=true
+
+# =============================================================================
+# DEVELOPMENT TOOLS (Development Only)
+# =============================================================================
+
+# Development editor and browser
+# EDITOR="code"
+# BROWSER="firefox"
+
+# =============================================================================
+# GIT HOOKS (Development Only)
+# =============================================================================
+
+# Git hooks configuration
+# PRE_COMMIT_ENABLED=true
+# AUTO_FORMAT=true
+# AUTO_LINT=true
+
+# =============================================================================
+# DOCUMENTATION
+# =============================================================================
+
+DOCS_AUTO_RELOAD=false
+API_DOCS_ENABLED=true
+SWAGGER_UI_ENABLED=true
+REDOC_ENABLED=true
+
+# =============================================================================
+# DEVELOPMENT OVERRIDES
+# =============================================================================
+# Uncomment the following lines for development:
+
+# DEBUG=true
+# ENVIRONMENT=development
+# LOG_LEVEL=debug
+# HOST=127.0.0.1
+# RELOAD=true
+# WORKERS=1
+# API_TITLE="${APP_NAME} Development"
+# API_VERSION="${APP_VERSION}-dev"
+# SECRET_KEY="dev-secret-key-change-in-production"
+# ALLOWED_HOSTS=["localhost", "127.0.0.1", "0.0.0.0", "::1"]
+# CORS_ORIGINS=["http://localhost:3000", "http://localhost:8000", "http://127.0.0.1:8000"]
+# ENABLE_API_METRICS=true
+# AUTO_RELOAD=true
+# RELOAD_DIRS=["backend", "frontend"]
+# RELOAD_DELAY=0.25
+# HOT_RELOAD=true
+# SOURCE_MAPS=true
+# MINIFY_ASSETS=false
+# COMPRESS_RESPONSES=false
+# SECURITY_HEADERS=false
+# HSTS_MAX_AGE=0
+# CSP_ENABLED=false
+# DOCS_AUTO_RELOAD=true