Enhance compose experience with comprehensive autocomplete systems

## Major Features Added

### Smart Mention Completion
- **Full fediverse handles**: @user@instance.com format instead of incomplete usernames
- **Multi-source suggestions**: Search API + followers + following for comprehensive results
- **Real-time API integration**: No more hardcoded sample data
- **Intelligent filtering**: Prefix-based matching across all user connections

### Comprehensive Emoji System
- **5,000+ Unicode emojis**: Complete emoji dataset via python-emoji library
- **Keyword-based search**: Find emojis by typing descriptive words (:fire, :heart, :grin)
- **Actual emoji insertion**: Inserts Unicode characters (🎃) not shortcodes (🎃)
- **Accurate selection**: Fixed bug where wrong emoji was inserted from autocomplete list
- **Smart synonyms**: Common aliases for frequently used emojis

### Enhanced ActivityPub Integration
- **Account relationships**: get_followers(), get_following(), search_accounts() methods
- **Expanded API coverage**: Better integration with fediverse social graph
- **Robust error handling**: Graceful fallbacks for API failures

### User Experience Improvements
- **Bug fixes**: Resolved autocomplete selection and focus restoration issues
- **Documentation**: Updated README with comprehensive feature descriptions
- **Dependencies**: Added emoji>=2.0.0 to requirements for Unicode support

## Technical Details
- Removed incomplete fallback data in favor of live API integration
- Improved completer selection logic to use actually selected items
- Enhanced error handling for network requests and API limitations
- Updated installation instructions for new emoji library dependency

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

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

src/activitypub/client.py

@@ -178,6 +178,35 @@ class ActivityPubClient:
         endpoint = f'/api/v1/accounts/{account_id}/unfollow'
         return self._make_request('POST', endpoint)
         
+    def get_followers(self, account_id: str, max_id: Optional[str] = None, limit: int = 40) -> List[Dict]:
+        """Get followers for an account"""
+        params = {'limit': limit}
+        if max_id:
+            params['max_id'] = max_id
+            
+        endpoint = f'/api/v1/accounts/{account_id}/followers'
+        return self._make_request('GET', endpoint, params=params)
+    
+    def get_following(self, account_id: str, max_id: Optional[str] = None, limit: int = 40) -> List[Dict]:
+        """Get accounts that an account is following"""
+        params = {'limit': limit}
+        if max_id:
+            params['max_id'] = max_id
+            
+        endpoint = f'/api/v1/accounts/{account_id}/following'
+        return self._make_request('GET', endpoint, params=params)
+    
+    def search_accounts(self, query: str, limit: int = 10) -> List[Dict]:
+        """Search for accounts by username"""
+        params = {
+            'q': query,
+            'type': 'accounts',
+            'limit': limit
+        }
+        
+        result = self._make_request('GET', '/api/v2/search', params=params)
+        return result.get('accounts', [])
+
     def search(self, query: str, account_id: Optional[str] = None, 
               max_id: Optional[str] = None, min_id: Optional[str] = None,
               type_filter: Optional[str] = None, limit: int = 20) -> Dict: