[feat] Update history API to v2 array format and add comprehensive tests

- Migrate from object-based to array-based history response format
- Update /history endpoint to /history_v2 with max_items parameter
- Add lazy loading of workflows via /history_v2/:prompt_id endpoint
- Implement comprehensive browser tests for history API functionality
- Add unit tests for API methods and queue store
- Update TaskItemImpl to support history workflow loading
- Add proper error handling and edge case coverage
- Follow established test patterns for better maintainability

This change improves performance by reducing initial payload size
and enables on-demand workflow loading for history items.

browser_tests/tests/sidebar/workflows.spec.ts

@@ -187,6 +187,7 @@ test.describe('Workflows sidebar', () => {
 
   test('Can save workflow as with same name', async ({ comfyPage }) => {
     await comfyPage.menu.topbar.saveWorkflow('workflow5.json')
+    await comfyPage.nextFrame()
     expect(await comfyPage.menu.workflowsTab.getOpenedWorkflowNames()).toEqual([
       'workflow5.json'
     ])