fix(ui): restore a green Frontend Quality job

[rennerdo30]

main has been red since late July. Every job except Frontend Quality passes on the current tip (2294805); Frontend Quality fails at its Lint step, which also hides two further breakages in the Test step behind it. This PR fixes all three, one commit per cause.

1. react-hooks lint errors (npm run lint, exit 1)

src/app/[locale]/errors/page.tsx
  43:14  error  Calling setState synchronously within an effect can trigger cascading renders  react-hooks/set-state-in-effect

src/components/file-upload.tsx
  71:58  error  Cannot access variable before it is declared  react-hooks/immutability

✖ 15 problems (2 errors, 13 warnings)

Both rules ship with the react-hooks plugin bundled by eslint-config-next 16.3.x. formatSize was duplicated verbatim in file-upload.tsx and file-browser.tsx, so it moves to lib/utils.ts as formatBytes (module scope, named constants, unit-tested) and both components consume it. The errors page moves to React Query, matching every other data-loading page in the app, which removes the offending effect rather than silencing it.

2. Radix primitives no longer expose displayName

Recent Radix releases (@radix-ui/react-label 2.1.15, react-select 2.3.7, react-tabs 1.1.21, …) dropped displayName from their primitives — grep -c displayName node_modules/@radix-ui/react-label/dist/index.mjs returns 0. Every wrapper that copied it (Label.displayName = LabelPrimitive.Root.displayName) therefore had undefined, failing 8 assertions and leaving anonymous ForwardRef nodes in React DevTools. Each wrapper now declares its own name, as the non-Radix ui components already did.

3. Popover dismissal is deferred to the following click

@radix-ui/react-popover now passes deferPointerDownOutside: true, so the dismissable layer waits for the click after an outside pointerdown (a drag ending outside no longer closes the popover). The test fired only pointerDown and never observed onOpenChange; it now simulates the full interaction.

Verification

Ran exactly what CI runs, from a clean origin/main checkout:

step	before	after
npm run lint	2 errors, 13 warnings — exit 1	0 errors, 13 warnings
npm run test:run	9 failed / 704 passed	716 passed (28 files)
npm run build	never reached	succeeds

The 13 remaining no-unused-vars warnings are pre-existing and non-fatal; they are left alone so this change stays scoped to the breakage.

Unblocks the open Dependabot PRs, which currently inherit this failure and cannot be judged on their own merits.