feat: comprehensive environment variable support

- Added support for 60+ environment variables covering all configuration options
- Created detailed documentation in docs/ENVIRONMENT_VARIABLES.md with tables
- Fixed missing skipStarredIssues field in GitHub config
- Updated docker-compose files to reference environment variable documentation
- Updated README to link to the new environment variables documentation
- Environment variables now populate UI configuration automatically on Docker startup
- Preserves manual UI changes when environment variables are not set
- Includes support for mirror metadata, scheduling, cleanup, and authentication options

Fixes #69

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

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

.env.example

@@ -30,41 +30,136 @@ DOCKER_IMAGE=arunavo4/gitea-mirror
 DOCKER_TAG=latest
 
 # ===========================================
-# MIRROR CONFIGURATION (Optional)
-# Can also be configured via web UI
+# GITHUB CONFIGURATION
+# All settings can also be configured via web UI
 # ===========================================
 
-# GitHub Configuration
+# Basic GitHub Settings
 # GITHUB_USERNAME=your-github-username
 # GITHUB_TOKEN=your-github-personal-access-token
-# SKIP_FORKS=false
+# GITHUB_TYPE=personal  # Options: personal, organization
+
+# Repository Selection
 # PRIVATE_REPOSITORIES=false
-# MIRROR_ISSUES=false
-# MIRROR_WIKI=false
+# PUBLIC_REPOSITORIES=true
+# INCLUDE_ARCHIVED=false
+# SKIP_FORKS=false
 # MIRROR_STARRED=false
+# STARRED_REPOS_ORG=starred  # Organization name for starred repos
+
+# Organization Settings
 # MIRROR_ORGANIZATIONS=false
 # PRESERVE_ORG_STRUCTURE=false
 # ONLY_MIRROR_ORGS=false
-# SKIP_STARRED_ISSUES=false
 
-# Gitea Configuration
+# Mirror Strategy
+# MIRROR_STRATEGY=preserve  # Options: preserve, single-org, flat-user, mixed
+
+# Advanced GitHub Settings
+# SKIP_STARRED_ISSUES=false  # Enable lightweight mode for starred repos
+
+# ===========================================
+# GITEA CONFIGURATION
+# All settings can also be configured via web UI
+# ===========================================
+
+# Basic Gitea Settings
 # GITEA_URL=http://gitea:3000
 # GITEA_TOKEN=your-local-gitea-token
 # GITEA_USERNAME=your-local-gitea-username
-# GITEA_ORGANIZATION=github-mirrors
-# GITEA_ORG_VISIBILITY=public
-# DELAY=3600
+# GITEA_ORGANIZATION=github-mirrors  # Default organization for single-org strategy
+
+# Repository Settings
+# GITEA_ORG_VISIBILITY=public  # Options: public, private, limited, default
+# GITEA_MIRROR_INTERVAL=8h  # Mirror sync interval (e.g., 30m, 1h, 8h, 24h)
+# GITEA_LFS=false  # Enable LFS support
+# GITEA_CREATE_ORG=true  # Auto-create organizations
+# GITEA_PRESERVE_VISIBILITY=false  # Preserve GitHub repo visibility in Gitea
+
+# Template Settings (for using repository templates)
+# GITEA_TEMPLATE_OWNER=template-owner
+# GITEA_TEMPLATE_REPO=template-repo
+
+# Topic Settings
+# GITEA_ADD_TOPICS=true  # Add topics to repositories
+# GITEA_TOPIC_PREFIX=gh-  # Prefix for topics
+
+# Fork Handling
+# GITEA_FORK_STRATEGY=reference  # Options: skip, reference, full-copy
 
 # ===========================================
-# OPTIONAL FEATURES
+# MIRROR OPTIONS
+# Control what gets mirrored from GitHub
 # ===========================================
 
-# Database Cleanup Configuration
+# Release and Metadata
+# MIRROR_RELEASES=false  # Mirror GitHub releases
+# MIRROR_WIKI=false  # Mirror wiki content
+
+# Issue Tracking (requires MIRROR_METADATA=true)
+# MIRROR_METADATA=false  # Master toggle for metadata mirroring
+# MIRROR_ISSUES=false  # Mirror issues
+# MIRROR_PULL_REQUESTS=false  # Mirror pull requests
+# MIRROR_LABELS=false  # Mirror labels
+# MIRROR_MILESTONES=false  # Mirror milestones
+
+# ===========================================
+# AUTOMATION CONFIGURATION
+# Schedule automatic mirroring
+# ===========================================
+
+# Basic Schedule Settings
+# SCHEDULE_ENABLED=false
+# SCHEDULE_INTERVAL=3600  # Interval in seconds or cron expression (e.g., "0 2 * * *")
+# DELAY=3600  # Legacy: same as SCHEDULE_INTERVAL, kept for backward compatibility
+
+# Execution Settings
+# SCHEDULE_CONCURRENT=false  # Allow concurrent mirror operations
+# SCHEDULE_BATCH_SIZE=10  # Number of repos to process in parallel
+# SCHEDULE_PAUSE_BETWEEN_BATCHES=5000  # Pause between batches (ms)
+
+# Retry Configuration
+# SCHEDULE_RETRY_ATTEMPTS=3
+# SCHEDULE_RETRY_DELAY=60000  # Delay between retries (ms)
+# SCHEDULE_TIMEOUT=3600000  # Max time for a mirror operation (ms)
+# SCHEDULE_AUTO_RETRY=true
+
+# Update Detection
+# SCHEDULE_ONLY_MIRROR_UPDATED=false  # Only mirror repos with updates
+# SCHEDULE_UPDATE_INTERVAL=86400000  # Check for updates interval (ms)
+# SCHEDULE_SKIP_RECENTLY_MIRRORED=true
+# SCHEDULE_RECENT_THRESHOLD=3600000  # Skip if mirrored within this time (ms)
+
+# Maintenance
+# SCHEDULE_CLEANUP_BEFORE_MIRROR=false  # Run cleanup before mirroring
+
+# Notifications
+# SCHEDULE_NOTIFY_ON_FAILURE=true
+# SCHEDULE_NOTIFY_ON_SUCCESS=false
+# SCHEDULE_LOG_LEVEL=info  # Options: error, warn, info, debug
+# SCHEDULE_TIMEZONE=UTC
+
+# ===========================================
+# DATABASE CLEANUP CONFIGURATION
+# Automatic cleanup of old events and data
+# ===========================================
+
+# Basic Cleanup Settings
 # CLEANUP_ENABLED=false
-# CLEANUP_RETENTION_DAYS=7
+# CLEANUP_RETENTION_DAYS=7  # Days to keep events
 
-# TLS/SSL Configuration
-# GITEA_SKIP_TLS_VERIFY=false  # WARNING: Only use for testing
+# Repository Cleanup
+# CLEANUP_DELETE_FROM_GITEA=false  # Delete repos from Gitea
+# CLEANUP_DELETE_IF_NOT_IN_GITHUB=true  # Delete if not in GitHub
+# CLEANUP_ORPHANED_REPO_ACTION=archive  # Options: skip, archive, delete
+# CLEANUP_DRY_RUN=true  # Test mode without actual deletion
+
+# Protected Repositories (comma-separated)
+# CLEANUP_PROTECTED_REPOS=important-repo,critical-project
+
+# Cleanup Execution
+# CLEANUP_BATCH_SIZE=10
+# CLEANUP_PAUSE_BETWEEN_DELETES=2000  # Pause between deletions (ms)
 
 # ===========================================
 # AUTHENTICATION CONFIGURATION
@@ -79,3 +174,9 @@ DOCKER_TAG=latest
 # HEADER_AUTH_AUTO_PROVISION=false
 # HEADER_AUTH_ALLOWED_DOMAINS=example.com,company.org
 
+# ===========================================
+# OPTIONAL FEATURES
+# ===========================================
+
+# TLS/SSL Configuration
+# GITEA_SKIP_TLS_VERIFY=false  # WARNING: Only use for testing