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/start-test-env.sh

@@ -0,0 +1,67 @@
+#!/bin/bash
+
+# Start test environment for manual testing
+
+cd "$(dirname "$0")"
+
+echo "🚀 Starting mail2couch test environment..."
+
+# Start containers
+echo "Starting containers..."
+podman-compose -f podman-compose.yml up -d
+
+# Wait for services
+echo "Waiting for services to be ready..."
+sleep 10
+
+# Check CouchDB
+echo "Checking CouchDB..."
+timeout=30
+while ! curl -s http://localhost:5984/_up > /dev/null 2>&1; do
+    timeout=$((timeout - 1))
+    if [ $timeout -le 0 ]; then
+        echo "❌ CouchDB failed to start"
+        exit 1
+    fi
+    sleep 1
+done
+echo "✅ CouchDB is ready at http://localhost:5984"
+
+# Check IMAP
+echo "Checking IMAP server..."
+timeout=30
+while ! nc -z localhost 3143 > /dev/null 2>&1; do
+    timeout=$((timeout - 1)) 
+    if [ $timeout -le 0 ]; then
+        echo "❌ IMAP server failed to start"
+        exit 1
+    fi
+    sleep 1
+done
+echo "✅ IMAP server is ready at localhost:3143"
+
+# Populate test data
+echo "Populating test messages..."
+./populate-test-messages.sh
+
+echo ""
+echo "🎉 Test environment is ready!"
+echo ""
+echo "Services:"
+echo "  - CouchDB: http://localhost:5984 (admin/password)"
+echo "  - CouchDB Web UI: http://localhost:5984/_utils"
+echo "  - IMAP Server: localhost:3143"
+echo "  - IMAPS Server: localhost:3993"
+echo "  - SMTP Server: localhost:3025"
+echo ""
+echo "Test accounts:"
+echo "  - testuser1:password123"
+echo "  - testuser2:password456"
+echo "  - syncuser:syncpass"
+echo "  - archiveuser:archivepass"
+echo ""
+echo "To run mail2couch:"
+echo "  cd ../go && ./mail2couch -config ../test/config-test.json"
+echo ""
+echo "To stop the environment:"
+echo "  ./stop-test-env.sh"