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/generate-ssl.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+
+# Generate SSL certificates for Dovecot testing
+
+set -e
+
+CERT_DIR="dovecot/ssl"
+mkdir -p "$CERT_DIR"
+
+# Generate DH parameters
+echo "Generating DH parameters..."
+openssl dhparam -out "$CERT_DIR/dh.pem" 2048
+
+# Generate private key
+echo "Generating private key..."
+openssl genrsa -out "$CERT_DIR/server.key" 2048
+
+# Generate certificate signing request
+echo "Generating certificate..."
+openssl req -new -key "$CERT_DIR/server.key" -out "$CERT_DIR/server.csr" -subj "/C=US/ST=Test/L=Test/O=Mail2Couch/CN=localhost"
+
+# Generate self-signed certificate
+openssl x509 -req -days 365 -in "$CERT_DIR/server.csr" -signkey "$CERT_DIR/server.key" -out "$CERT_DIR/server.crt"
+
+# Clean up CSR
+rm "$CERT_DIR/server.csr"
+
+echo "SSL certificates generated successfully in $CERT_DIR/"