feat(users): per-user library assignment + themed confirm modal (#222)

Adds Navidrome library assignment to the User Management settings
panel: GET /api/library + PUT /api/user/{id}/library wired through
new Rust commands. UserForm gets a checkbox picker (hidden for
admins, who auto-receive all libraries server-side) with inline
validation. User rows compacted to a single clickable line with
hover highlight; native confirm() replaced by a portal-based
ConfirmModal (theme-aware, ESC/Enter, vertically centered).

Co-authored-by: Psychotoxical <dev@psysonic.app>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/locales/nb.ts

@@ -473,6 +473,12 @@ export const nbTranslation = {
     userMgmtPassword: 'Passord',
     userMgmtPasswordEditHint: 'Skriv inn et nytt passord for å oppdatere det.',
     userMgmtRoleAdmin: 'Admin',
+    userMgmtLibraries: 'Biblioteker',
+    userMgmtLibrariesAdminHint: 'Administratorbrukere har automatisk tilgang til alle biblioteker.',
+    userMgmtLibrariesEmpty: 'Ingen biblioteker tilgjengelig på denne serveren.',
+    userMgmtLibrariesValidation: 'Velg minst ett bibliotek.',
+    userMgmtLibrariesUpdateError: 'Brukeren ble lagret, men bibliotekstilordning mislyktes',
+    userMgmtNoLibraries: 'Ingen biblioteker tilordnet',
     userMgmtSave: 'Lagre',
     userMgmtCancel: 'Avbryt',
     userMgmtDelete: 'Slett',