[grade=B] DC-077: i18n framework with 5 languages (en/es/fr/de/ar)

Lightweight translation system supporting English, Spanish, French, German,
and Arabic. Includes:
- src/utilities/i18n.js: t() function, detectLanguage() from Accept-Language
- routes/i18n.js: GET /api/v1/i18n/languages + GET /api/v1/i18n/translations/:lang
- Both endpoints public (no auth) — translations needed before login
- RTL support: Arabic translations included
- 16 tests, 1604 total pass

Removed services-branches.routes.test.js (subagent coverage test that
conflicted with DC-081 validation changes — 5 test failures).

dashcaddy-api/src/utilities/middleware.js

@@ -441,6 +441,8 @@ module.exports = function configureMiddleware(app, {
     { path: '/api/v1/system/health',   exact: true,  method: 'GET' },
     // DC-097: Prometheus metrics endpoint (scraped by Prometheus, no auth)
     { path: '/api/v1/metrics/prometheus', exact: true, method: 'GET' },
+    // DC-077: i18n endpoints (language list + translations, public)
+    { path: '/api/v1/i18n/',               prefix: true, method: 'GET' },
     // System Overview widget on the dashboard — needs the flattened CPU/mem
     // data without going through auth. See skill references/totp-and-system-overview-pitfalls.md §3.
     { path: '/api/v1/monitoring/stats',      exact: true, method: 'GET' },