Implement Fallback Tag Display in GUI

## Motivation

The current GUI tag display logic assumes all image tags can be parsed into structured platform/version components. With the relaxed validation policy, some tags may not conform to the expected structure and should be displayed as single raw labels instead of attempting forced parsing. This requires updating the frontend display logic to gracefully handle both structured and unstructured tag formats.

## Required Features

- **Smart tag detection**: Determine whether tags can be parsed into structured components
- **Fallback display**: Show unparseable tags as single readable labels
- **Consistent styling**: Maintain visual consistency between structured and fallback displays
- **User experience**: Ensure users can easily understand both display modes
- **Performance**: Avoid unnecessary parsing attempts for obviously unstructured tags

## Impact

### Primary Components

- Frontend tag parsing and display components
- Image metadata processing logic that determines display mode
- GUI components that render image tag information

### Secondary Components

- Image list views in admin interface
- Session creation dialogs showing available images
- Image selection forms and dropdowns
- Customized image management interfaces

### Services Affected

- WebUI tag rendering components
- GraphQL resolvers providing image tag data
- REST API endpoints that format tag information

## Testing Scenarios

### Display Mode Tests

- Verify structured tags show as multiple labels (platform + version)
- Confirm unstructured tags display as single readable labels
- Test mixed repositories with both tag types display correctly
- Validate fallback styling matches design consistency

### Edge Case Handling

- Very long tag names are truncated appropriately
- Special characters in tag names don't break display
- Empty or null tag values are handled gracefully
- Unicode characters in tags render correctly

### User Experience Tests

- Users can easily identify platform and version from structured tags
- Fallback tags remain readable and informative
- Color coding and styling provide clear visual hierarchy
- Tooltips or hover states provide additional context when needed

### Performance Tests

- Tag parsing doesn't cause UI lag with large image lists
- Fallback detection is fast for obviously unstructured tags
- Memory usage remains stable with mixed tag display modes

JIRA Issue: BA-2462