feat(i18n): translate remaining components (HU/EN/DE)

Feed, VideoCard, Sidebar, PlayerModal, Channels, Stats, SettingsPanel,
OnboardingWizard, NotificationCenter, Toaster, ErrorBoundary and the relativeTime
helper are now fully translated in Hungarian, English and German, each with its own
locale area file (auto-loaded). Key parity verified across all three languages.

frontend/src/i18n/locales/hu/time.json

@@ -0,0 +1,10 @@
+{
+  "justNow": "épp most",
+  "secondsAgo": "{{count}} mp-e",
+  "minutesAgo": "{{count}} perce",
+  "hoursAgo": "{{count}} órája",
+  "daysAgo": "{{count}} napja",
+  "weeksAgo": "{{count}} hete",
+  "monthsAgo": "{{count}} hónapja",
+  "yearsAgo": "{{count}} éve"
+}