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/dovecot/entrypoint.sh

@@ -0,0 +1,51 @@
+#!/bin/sh
+
+# Entrypoint script for Dovecot test container
+
+set -e
+
+echo "Installing Dovecot..."
+apk add --no-cache dovecot dovecot-lmtpd openssl
+
+echo "Setting up directories..."
+mkdir -p /var/mail
+mkdir -p /var/run/dovecot
+mkdir -p /var/log/dovecot
+
+# Create dovecot user if it doesn't exist
+if ! getent passwd dovecot > /dev/null 2>&1; then
+    addgroup -g 97 dovecot
+    adduser -D -u 97 -G dovecot -s /sbin/nologin dovecot
+fi
+
+# Set proper ownership
+chown -R dovecot:dovecot /var/mail
+chown -R dovecot:dovecot /var/run/dovecot
+chown -R root:dovecot /etc/dovecot
+chmod -R 0640 /etc/dovecot
+chmod 0644 /etc/dovecot/dovecot.conf
+
+# Generate SSL certificates if they don't exist
+if [ ! -f /etc/dovecot/ssl/server.crt ] || [ ! -f /etc/dovecot/ssl/server.key ]; then
+    echo "Generating SSL certificates..."
+    mkdir -p /etc/dovecot/ssl
+    
+    # Generate DH parameters (small for testing)
+    openssl dhparam -out /etc/dovecot/ssl/dh.pem 1024
+    
+    # Generate private key
+    openssl genrsa -out /etc/dovecot/ssl/server.key 2048
+    
+    # Generate certificate
+    openssl req -new -key /etc/dovecot/ssl/server.key -out /etc/dovecot/ssl/server.csr -subj "/C=US/ST=Test/L=Test/O=Mail2Couch/CN=localhost"
+    openssl x509 -req -days 365 -in /etc/dovecot/ssl/server.csr -signkey /etc/dovecot/ssl/server.key -out /etc/dovecot/ssl/server.crt
+    rm /etc/dovecot/ssl/server.csr
+fi
+
+# Ensure SSL directory permissions
+chown -R dovecot:dovecot /etc/dovecot/ssl
+chmod 600 /etc/dovecot/ssl/server.key
+chmod 644 /etc/dovecot/ssl/server.crt
+
+echo "Starting Dovecot..."
+exec dovecot -F