fix(e2e): restore the frontend build by typing the responses findOrFail searches (#254)

main did not build, so every Portainer deploy failed with `npm run build` exit code 2. My regression from #241.

findOrFail<T>(items: T[], predicate: (item: T) => boolean) infers T from both parameters. The call sites annotate the predicate as documentation, and the arrays come from .json(), which is any and offers no competing candidate — so T became the one-field shape written in the lambda and every caller failed on the field it actually wanted. Array.prototype.find has no such problem, which is why the code this replaced type-checked.

The four responses are now typed at their call sites, so T is inferred from real data and the predicates need no annotation. findOrFail additionally takes NoInfer<T> on its predicate, so a stray annotation can never drive the element type again. The specs are better typed than before this change: `.json()` was plain any, and the annotations only ever documented a shape nothing enforced.

I did not catch this because I verified with a bare `npx tsc --noEmit`, and tsconfig.json is `"include": ["src"]` — it structurally cannot see tests/. The specs are checked by the second command in `npm run build`, which is the step Docker runs and the step that failed. Verified this time with `npm run build` itself, plus lint, the unit suite, and two consecutive full e2e passes.

Closes #254

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/tests/e2e/admin-inline-category.spec.ts

@@ -31,12 +31,14 @@ test.describe('Inline category creation from the item form', () => {
     await adminInventory.confirmButton.click();
     await expect(page.getByText('Item added')).toBeVisible();
 
-    const items = await (await page.request.get('/api/admin/items')).json();
+    const items: { name: string; category_name: string | null }[] = await (
+      await page.request.get('/api/admin/items')
+    ).json();
     // findOrFail already fails with the row count when the item is missing,
     // which the toBeTruthy assertion this replaces could not report.
     const saved = findOrFail(
       items,
-      (item: { name: string }) => item.name === itemName,
+      (item) => item.name === itemName,
       `the item named ${itemName}`
     );
     expect(saved.category_name).toBe(categoryName);