temiport25: NavBar i18n + memoization

[temiport25]

Internationalizes the remaining hard-coded NavBar copy (#805) and memoizes the component's computations (#807).

• Add i18n translations for NavBar #805 i18n — the mainnet badge, the "Retry Queue" link and the "admin" role badge were hard-coded English. They now go through t('common.mainnet'), t('common.retryQueue') and t('common.admin') so all three locales cover them.
• Memoize expensive computations in NavBar #807 memoization — the component is wrapped in React.memo; isAdmin is a useMemo derivation, handleLogout is a useCallback, and the public/admin link lists are useMemo-built so a parent layout re-render no longer re-computes them (proven in the test via the useSession call count).

Adds tests/navbar-i18n-memo.test.tsx (6 tests) with a t spy asserting the requested keys. Note: the i18n message bundles are corrupted in this checkout (binary), so the provider is mocked; repo-wide tsc/vitest failures are pre-existing and unrelated.

Closes #804
Closes #805
Closes #806
Closes #807

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