feat: implement real IMAP message parsing with native CouchDB attachments

- Replace placeholder message generation with actual IMAP message fetching using go-message library
- Add per-account CouchDB databases for better organization and isolation
- Implement native CouchDB attachment storage with proper revision management
- Add command line argument parsing with --max-messages flag for controlling message processing limits
- Support both sync and archive modes with proper document synchronization
- Add comprehensive test environment with Podman containers (GreenMail IMAP server + CouchDB)
- Implement full MIME multipart parsing for proper body and attachment extraction
- Add TLS and plain IMAP connection support based on port configuration
- Update configuration system to support sync vs archive modes
- Create test scripts and sample data for development and testing

Key technical improvements:
- Real email envelope and header processing with go-imap v2 API
- MIME Content-Type and Content-Disposition parsing for attachment detection
- CouchDB document ID generation using mailbox_uid format for uniqueness
- Duplicate detection and prevention to avoid re-storing existing messages
- Proper error handling and connection management for IMAP operations

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

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

test/README.md

@@ -0,0 +1,150 @@
+# mail2couch Test Environment
+
+This directory contains a complete test environment for mail2couch using Podman containers.
+
+## Overview
+
+The test environment provides:
+- **CouchDB**: Database for storing email messages
+- **GreenMail IMAP Server**: Java-based mail server designed for testing with pre-populated test accounts and messages
+- **Test Configuration**: Ready-to-use config for testing both sync and archive modes
+
+## Quick Start
+
+### Run Full Integration Tests
+```bash
+./run-tests.sh
+```
+This will:
+1. Start all containers
+2. Populate test data
+3. Run mail2couch
+4. Verify results
+5. Clean up
+
+### Manual Testing
+```bash
+# Start test environment
+./start-test-env.sh
+
+# Run mail2couch manually
+cd ../go
+./mail2couch -config ../test/config-test.json
+
+# Stop test environment when done
+cd ../test
+./stop-test-env.sh
+```
+
+## Test Accounts
+
+The test environment includes these IMAP accounts:
+
+| Username | Password | Mode | Purpose |
+|----------|----------|------|---------|
+| `testuser1` | `password123` | archive | General archive testing |
+| `testuser2` | `password456` | - | Additional test user |
+| `syncuser` | `syncpass` | sync | Testing sync mode (1-to-1) |
+| `archiveuser` | `archivepass` | archive | Testing archive mode |
+
+Each account contains:
+- 10 messages in INBOX (every 3rd has an attachment)
+- 3 messages in Sent folder
+- Various message types for comprehensive testing
+
+## Services
+
+### CouchDB
+- **URL**: http://localhost:5984
+- **Admin**: `admin` / `password`
+- **Web UI**: http://localhost:5984/_utils
+
+### GreenMail Server
+- **Host**: localhost
+- **IMAP Port**: 3143 (plain)
+- **IMAPS Port**: 3993 (SSL)
+- **SMTP Port**: 3025
+- **Server**: GreenMail (Java-based test server)
+
+## Database Structure
+
+mail2couch will create separate databases for each mail source:
+- `test_user_1` - Test User 1 (archive mode)
+- `test_sync_user` - Test Sync User (sync mode)  
+- `test_archive_user` - Test Archive User (archive mode)
+
+## Testing Sync vs Archive Modes
+
+### Sync Mode (`syncuser`)
+- Database exactly matches mail account
+- If messages are deleted from IMAP, they're removed from CouchDB
+- 1-to-1 relationship
+
+### Archive Mode (`archiveuser`, `testuser1`)
+- Database preserves all messages ever seen
+- Messages deleted from IMAP remain in CouchDB
+- Archive/backup behavior
+
+## File Structure
+
+```
+test/
+├── podman-compose.yml          # Container orchestration
+├── config-test.json            # Test configuration
+├── run-tests.sh               # Full integration test
+├── start-test-env.sh          # Start environment
+├── stop-test-env.sh           # Stop environment
+├── generate-ssl.sh            # Generate SSL certificates
+├── populate-test-messages.sh  # Create test messages
+├── dovecot/
+│   ├── dovecot.conf          # Dovecot configuration
+│   ├── users                 # User database
+│   ├── passwd                # Password database
+│   └── ssl/                  # SSL certificates
+└── README.md                 # This file
+```
+
+## Prerequisites
+
+- Podman and podman-compose
+- OpenSSL (for certificate generation)
+- curl and nc (for connectivity checks)
+- Go (for building mail2couch)
+
+## Troubleshooting
+
+### Containers won't start
+```bash
+# Check podman status
+podman ps -a
+
+# View logs
+podman logs mail2couch_test_couchdb
+podman logs mail2couch_test_imap
+```
+
+### CouchDB connection issues
+- Verify CouchDB is running: `curl http://localhost:5984`
+- Check admin credentials: `admin/password`
+
+### IMAP connection issues
+- Test IMAP connection: `nc -z localhost 143`
+- Check Dovecot logs: `podman logs mail2couch_test_imap`
+
+### Permission issues
+- Ensure scripts are executable: `chmod +x *.sh`
+- Check file permissions in dovecot directory
+
+## Advanced Usage
+
+### Add custom test messages
+Edit `populate-test-messages.sh` to create additional test scenarios.
+
+### Modify IMAP configuration
+Edit `dovecot/dovecot.conf` and restart containers.
+
+### Test with SSL
+Update `config-test.json` to use port 993 and enable SSL.
+
+### Custom test scenarios
+Create additional configuration files for specific test cases.