Implement comprehensive tag management features in PhotoTagger

Add functionality for deduplicating tags, parsing tag strings, and managing tag IDs within the PhotoTagger GUI. Introduce a tag management dialog for adding, editing, and deleting tags, ensuring a user-friendly interface for tag operations. Update the internal logic to utilize tag IDs for improved performance and reliability, while enhancing the README to reflect these significant changes in tag handling and management.

README.md

@@ -192,6 +192,9 @@ This GUI provides a file explorer-like interface for managing photo tags with ad
 - 📱 **Responsive Layout** - Adapts to window size with proper scrolling
 - 🎨 **Modern Interface** - Clean, intuitive design with visual feedback
 - ⚡ **Fast Performance** - Optimized for large photo collections
+- 🏷️ **Smart Tag Management** - Duplicate tag prevention with silent handling
+- 🔄 **Accurate Change Tracking** - Only counts photos with actual new tags as "changed"
+- 🎯 **Reliable Tag Operations** - Uses tag IDs internally for consistent, bug-free behavior
 
 **📋 Available View Modes:**
 
@@ -397,6 +400,8 @@ The tool uses SQLite database (`data/photos.db` by default) with these tables:
 - **No Duplicate Tags** - Unique constraint prevents duplicate tag-photo combinations
 - **Optimized Queries** - Efficient indexing and query patterns for fast performance
 - **Data Integrity** - Proper foreign key relationships and constraints
+- **Tag ID-Based Operations** - All tag operations use efficient ID-based lookups instead of string comparisons
+- **Robust Tag Handling** - Eliminates string parsing issues and edge cases in tag management
 
 ## ⚙️ Configuration
 
@@ -774,6 +779,18 @@ This is now a minimal, focused tool. Key principles:
 - ✅ **Unique Constraint Update** - Prevents duplicate people with same combination of all five fields
 - ✅ **Streamlined Data Entry** - All name fields are now simple text inputs for faster typing
 
+### 🏷️ Tag System Improvements (NEW!)
+- ✅ **Tag ID-Based Architecture** - Complete refactoring to use tag IDs internally instead of tag names
+- ✅ **Eliminated String Parsing Issues** - No more problems with empty strings, whitespace, or parsing errors
+- ✅ **Improved Performance** - Tag ID comparisons are faster than string comparisons
+- ✅ **Better Reliability** - No case sensitivity issues or string parsing bugs
+- ✅ **Database Efficiency** - Direct ID operations instead of string lookups
+- ✅ **Cleaner Architecture** - Clear separation between internal logic (IDs) and display (names)
+- ✅ **Duplicate Prevention** - Silent prevention of duplicate tags without warning messages
+- ✅ **Accurate Change Counting** - Only photos with actual new tags are counted as "changed"
+- ✅ **Robust Tag Parsing** - Handles edge cases like empty tag strings and malformed data
+- ✅ **Consistent Behavior** - All tag operations use the same reliable logic throughout the application
+
 ### 🎨 Enhanced Modify Identified Interface (NEW!)
 - ✅ **Complete Person Information** - Shows full names with middle names, maiden names, and birth dates
 - ✅ **Last Name Search** - Filter people by last name with case-insensitive search