fix(desktop): load server language packs for embedded file surfaces

[chengjie]

The desktop file explorer can stay in English/Turkish even when the account uses an installed server language pack. The shell fetches branding through IPC, but never populates the bundled explorer's locale registry, and passes its native-chrome fallback instead of the account language.

Load the active server's language list before mounting, exporting the loader from the same source registry as the bundled explorer. Pass the account language to the explorer and connections panel, including changes between pack languages while native chrome stays English. Accept language tags through the existing settings bridge and server API. Native menus keep their built-in fallback.

Clear the previous server's language list on a server switch and ignore stale branding responses, including after reset. Failures retain built-in fallback. No translations, branding, dependencies or database changes.

Validation (macOS arm64, Node 22 / pnpm 9.12.0 / Go 1.25.14):

• New desktop regressions fail on the original implementation and pass with the fix; 12 desktop language tests pass.
• Language registry Vitest suite: 19 pass, including server switches, delayed responses and failure fallback.
• Full packages, web, sync:embed and backend build passes; check:embed confirms 638 admin and 105 web-component files match.
• Desktop typecheck and build pass.
• Full desktop suite: 450 pass, 4 file-watcher timeouts in openwith-outside.test.ts. The same four failures reproduce on pristine v0.57.0; the relevant source/test files are unchanged through this PR base. No assertions relaxed.

Not run: packaged Electron interactive E2E, Windows/Linux installation or full backend tests. The uploaded branch was fetched and its tree verified identical to the locally tested commit.

[brkfun]

Thanks a lot, @chengjie! This went out with filex 0.57.2: the desktop app's file list and connections panel now follow the account's language when it comes from a server language pack, and a server switch no longer carries the previous server's languages over.

We built on your loader afterwards: the desktop app now gives up on a server's language list after ten seconds instead of staying on "Connecting", in 0.57.3, which goes out today.

Thank you for this one, and for the careful report in #123. Its fix is in 0.57.3 too.