feat: add comprehensive README documentation and clean up configuration

## Documentation Enhancements
- Create comprehensive README with installation, configuration, and usage examples
- Add simple, advanced, and provider-specific configuration examples
- Document all features: incremental sync, wildcard patterns, keyword filtering, attachment support
- Include production deployment guidance and troubleshooting section
- Add architecture documentation with database structure and document format examples

## Configuration Cleanup
- Remove unnecessary `database` field from CouchDB configuration
- Add `m2c_` prefix to all CouchDB database names for better namespace isolation
- Update GenerateAccountDBName() to consistently prefix databases with `m2c_`
- Clean up all configuration examples to remove deprecated database field

## Test Environment Simplification
- Simplify test script structure to eliminate confusion and redundancy
- Remove redundant populate-test-messages.sh wrapper script
- Update run-tests.sh to be comprehensive automated test with cleanup
- Maintain clear separation: automated tests vs manual testing environment
- Update all test scripts to expect m2c-prefixed database names

## Configuration Examples Added
- config-simple.json: Basic single Gmail account setup
- config-advanced.json: Multi-account with complex filtering and different providers
- config-providers.json: Real-world configurations for Gmail, Outlook, Yahoo, iCloud

## Benefits
- Clear documentation for users from beginner to advanced
- Namespace isolation prevents database conflicts in shared CouchDB instances
- Simplified test workflow eliminates user confusion about which scripts to use
- Comprehensive examples cover common email provider configurations

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

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

config-simple.json

@@ -0,0 +1,26 @@
+{
+  "couchDb": {
+    "url": "http://localhost:5984",
+    "user": "admin",
+    "password": "password"
+  },
+  "mailSources": [
+    {
+      "name": "Personal Gmail",
+      "enabled": true,
+      "protocol": "imap",
+      "host": "imap.gmail.com",
+      "port": 993,
+      "user": "your-email@gmail.com",
+      "password": "your-app-password",
+      "mode": "archive",
+      "folderFilter": {
+        "include": ["INBOX", "Sent"],
+        "exclude": []
+      },
+      "messageFilter": {
+        "since": "2024-01-01"
+      }
+    }
+  ]
+}