Add public changelog with Atom feed and What's New indicator

- Changelog entries authored as markdown files in apps/journal/changelog/
  with YAML frontmatter, loaded via Vite import.meta.glob at build time
- /changelog list page with date, title, and preview
- /changelog/:slug detail page with full markdown rendering (react-markdown)
  and Open Graph meta tags for social sharing
- /changelog/feed.xml Atom feed with auto-discovery <link> tags
- "What's New" dot on nav bar using localStorage timestamp tracking
- Notification toggle: users can permanently disable/re-enable the indicator
- i18n strings for en and de
- Initial changelog entry covering the Phase 1 launch

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/i18n/src/locales/de.ts

@@ -192,9 +192,16 @@ export default {
       previous: "Zurück",
       next: "Weiter",
     },
+    changelog: {
+      title: "Änderungsprotokoll",
+      subtitle: "Was gibt es Neues auf trails.cool",
+      backToList: "Zurück zum Änderungsprotokoll",
+      showNotifications: "Über neue Einträge benachrichtigen",
+    },
     nav: {
       routes: "Routen",
       activities: "Aktivitäten",
+      changelog: "Änderungen",
       login: "Anmelden",
       register: "Registrieren",
       profile: "Profil",

packages/i18n/src/locales/en.ts

@@ -192,9 +192,16 @@ export default {
       previous: "Previous",
       next: "Next",
     },
+    changelog: {
+      title: "Changelog",
+      subtitle: "What's new on trails.cool",
+      backToList: "Back to Changelog",
+      showNotifications: "Notify me of new entries",
+    },
     nav: {
       routes: "Routes",
       activities: "Activities",
+      changelog: "Changelog",
       login: "Sign In",
       register: "Register",
       profile: "Profile",