feat: add checkpoint hash filtering and navigation

- Add checkpoint hash parameter parsing to backend routes
- Implement checkpoint hash filtering in frontend API client
- Add click navigation from recipe modal to checkpoints page
- Update checkpoint items to use pointer cursor for better UX

Checkpoint items in recipe modal are now clickable and will navigate to the checkpoints page with appropriate hash filtering applied. This improves user workflow when wanting to view checkpoint details from recipes.

tests/frontend/components/pageControls.filtering.test.js

@@ -62,6 +62,8 @@ vi.mock('../../../static/js/utils/updateCheckHelpers.js', () => ({
 beforeEach(() => {
   vi.resetModules();
   vi.clearAllMocks();
+  localStorage.clear();
+  sessionStorage.clear();
 
   loadMoreWithVirtualScrollMock.mockResolvedValue(undefined);
   refreshModelsMock.mockResolvedValue(undefined);
@@ -163,6 +165,8 @@ function renderControlsDom(pageKey) {
     </div>
     <div id="customFilterIndicator" class="control-group hidden">
       <div class="filter-active">
+        <i class="fas fa-filter"></i>
+        <span class="customFilterText" title=""></span>
         <i class="fas fa-times-circle clear-filter"></i>
       </div>
     </div>
@@ -518,6 +522,35 @@ describe('PageControls favorites, sorting, and duplicates scenarios', () => {
     expect(stateModule.getCurrentPageState().sortBy).toBe('date:desc');
   });
 
+  it('shows checkpoint custom filter indicator from recipes and clears it', async () => {
+    renderControlsDom('checkpoints');
+    const stateModule = await import('../../../static/js/state/index.js');
+    stateModule.initPageState('checkpoints');
+
+    sessionStorage.setItem('lora_manager_recipe_to_checkpoint_filterHash', 'abc123');
+    sessionStorage.setItem('lora_manager_filterCheckpointRecipeName', 'Flux Recipe With Long Name');
+
+    const { CheckpointsControls } = await import('../../../static/js/components/controls/CheckpointsControls.js');
+
+    const controls = new CheckpointsControls();
+
+    const indicator = document.getElementById('customFilterIndicator');
+    expect(indicator.classList.contains('hidden')).toBe(false);
+
+    const filterText = indicator.querySelector('.customFilterText');
+    expect(filterText.textContent.startsWith('Viewing checkpoint from:')).toBe(true);
+    expect(filterText.getAttribute('title')).toBe('Viewing checkpoint from: Flux Recipe With Long Name');
+
+    resetAndReloadMock.mockClear();
+
+    await controls.clearCustomFilter();
+
+    expect(sessionStorage.getItem('lora_manager_recipe_to_checkpoint_filterHash')).toBeNull();
+    expect(sessionStorage.getItem('lora_manager_filterCheckpointRecipeName')).toBeNull();
+    expect(indicator.classList.contains('hidden')).toBe(true);
+    expect(resetAndReloadMock).toHaveBeenCalled();
+  });
+
   it('updates duplicate badge after refresh and toggles duplicate mode from controls', async () => {
     renderControlsDom('checkpoints');
     const stateModule = await import('../../../static/js/state/index.js');