feat: implement comprehensive wildcard folder selection and keyword filtering

## Wildcard Folder Selection
- Add support for wildcard patterns (`*`, `?`, `[abc]`) using filepath.Match
- Implement special case: `"*"` selects ALL available folders
- Support for complex include/exclude pattern combinations
- Maintain backwards compatibility with exact string matching
- Enable subfolder pattern matching (e.g., `Work/*`, `*/Drafts`)

## Keyword Filtering
- Add SubjectKeywords, SenderKeywords, RecipientKeywords to MessageFilter config
- Implement case-insensitive keyword matching across message fields
- Support multiple keywords per filter type with inclusive OR logic
- Add ShouldProcessMessage method for message-level filtering

## Enhanced Test Environment
- Create comprehensive wildcard pattern test scenarios
- Add 12 test folders covering various pattern types: Work/*, Important/*, Archive/*, exact matches
- Implement dedicated wildcard test script (test-wildcard-patterns.sh)
- Update test configurations to demonstrate real-world wildcard usage patterns
- Enhance test data generation with folder-specific messages for validation

## Documentation
- Create FOLDER_PATTERNS.md with comprehensive wildcard examples and use cases
- Update CLAUDE.md to reflect all implemented features and current status
- Enhance test README with detailed wildcard pattern explanations
- Provide configuration examples for common email organization scenarios

## Message Origin Tracking
- Verify all messages in CouchDB properly tagged with origin folder in `mailbox` field
- Maintain per-account database isolation for better organization
- Document ID format: `{folder}_{uid}` ensures uniqueness across folders

Key patterns supported:
- `["*"]` - All folders (with excludes)
- `["Work*", "Important*"]` - Prefix matching
- `["Work/*", "Archive/*"]` - Subfolder patterns
- `["INBOX", "Sent"]` - Exact matches
- Complex include/exclude combinations

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

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

test/README.md

@@ -22,6 +22,16 @@ This will:
 4. Verify results
 5. Clean up
 
+### Run Wildcard Pattern Tests
+```bash
+./test-wildcard-patterns.sh
+```
+This will test various wildcard folder patterns including:
+- `*` (all folders)
+- `Work*` (prefix patterns)
+- `*/Drafts` (subfolder patterns)
+- Complex include/exclude combinations
+
 ### Manual Testing
 ```bash
 # Start test environment
@@ -40,17 +50,18 @@ cd ../test
 
 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 |
+| Username | Password | Mode | Folder Pattern | Purpose |
+|----------|----------|------|---------------|---------|
+| `testuser1` | `password123` | archive | `*` (exclude Drafts, Trash) | Wildcard all folders test |
+| `syncuser` | `syncpass` | sync | `Work*`, `Important*`, `INBOX` | Work pattern test |
+| `archiveuser` | `archivepass` | archive | `INBOX`, `Sent`, `Personal` | Specific folders test |
+| `testuser2` | `password456` | archive | `Work/*`, `Archive/*` | Subfolder pattern test |
 
 Each account contains:
 - 10 messages in INBOX (every 3rd has an attachment)
-- 3 messages in Sent folder
-- Various message types for comprehensive testing
+- 3 messages in each additional folder
+- Test folders: `Sent`, `Work/Projects`, `Work/Archive`, `Work/Temp`, `Personal`, `Important/Urgent`, `Important/Meetings`, `Archive/2024`, `Archive/Projects`, `Archive/Drafts`, `Drafts`, `Trash`
+- Various message types for comprehensive wildcard testing
 
 ## Services
 
@@ -69,9 +80,15 @@ Each account contains:
 ## 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)
+- `wildcard_all_folders_test` - Wildcard All Folders Test (archive mode)
+- `work_pattern_test` - Work Pattern Test (sync mode)  
+- `specific_folders_only` - Specific Folders Only (archive mode)
+- `subfolder_pattern_test` - Subfolder Pattern Test (archive mode)
+
+Each database contains documents with:
+- `mailbox` field indicating the origin folder
+- Native CouchDB attachments for email attachments
+- Full message headers and body content
 
 ## Testing Sync vs Archive Modes
 
@@ -85,22 +102,68 @@ mail2couch will create separate databases for each mail source:
 - Messages deleted from IMAP remain in CouchDB
 - Archive/backup behavior
 
+## Wildcard Pattern Examples
+
+The test environment demonstrates these wildcard patterns:
+
+### All Folders Pattern (`*`)
+```json
+{
+  "folderFilter": {
+    "include": ["*"],
+    "exclude": ["Drafts", "Trash"]
+  }
+}
+```
+Processes all folders except Drafts and Trash.
+
+### Work Pattern (`Work*`)
+```json
+{
+  "folderFilter": {
+    "include": ["Work*", "Important*", "INBOX"],
+    "exclude": ["*Temp*"]
+  }
+}
+```
+Includes Work/Projects, Work/Archive, Important/Urgent, Important/Meetings, and INBOX. Excludes Work/Temp.
+
+### Specific Folders
+```json
+{
+  "folderFilter": {
+    "include": ["INBOX", "Sent", "Personal"],
+    "exclude": []
+  }
+}
+```
+Only processes the exact named folders.
+
+### Subfolder Pattern (`Work/*`)
+```json
+{
+  "folderFilter": {
+    "include": ["Work/*", "Archive/*"],
+    "exclude": ["*/Drafts"]
+  }
+}
+```
+Includes all subfolders under Work and Archive, but excludes any Drafts subfolder.
+
 ## File Structure
 
 ```
 test/
 ├── podman-compose.yml          # Container orchestration
-├── config-test.json            # Test configuration
+├── config-test.json            # Main test configuration with wildcard examples
+├── config-wildcard-examples.json # Advanced wildcard patterns
+├── test-wildcard-patterns.sh   # Wildcard pattern testing script
 ├── 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
+├── populate-greenmail.py      # Create test messages with folders
+├── populate-test-messages.sh  # Wrapper script
+├── dovecot/                   # Dovecot configuration (legacy)
 └── README.md                 # This file
 ```