Add CivitAI re-linking functionality and related UI components. Fixes #216

- Implemented new API endpoints for re-linking models to CivitAI.
- Added context menu options for re-linking in both Lora and Checkpoint context menus.
- Created a modal for user confirmation and input for CivitAI model URL.
- Updated styles for the new modal and context menu items.
- Enhanced error handling and user feedback during the re-linking process.

templates/checkpoints.html

@@ -18,6 +18,7 @@
     <!-- <div class="context-menu-item" data-action="details"><i class="fas fa-info-circle"></i> View Details</div> -->
     <div class="context-menu-item" data-action="civitai"><i class="fas fa-external-link-alt"></i> View on CivitAI</div>
     <div class="context-menu-item" data-action="refresh-metadata"><i class="fas fa-sync"></i> Refresh Civitai Data</div>
+    <div class="context-menu-item" data-action="relink-civitai"><i class="fas fa-link"></i> Re-link to Civitai</div>
     <div class="context-menu-item" data-action="copyname"><i class="fas fa-copy"></i> Copy Model Filename</div>
     <div class="context-menu-item" data-action="preview"><i class="fas fa-folder-open"></i> Open Examples Folder</div>
     <div class="context-menu-item" data-action="replace-preview"><i class="fas fa-image"></i> Replace Preview</div>