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>

apps/journal/app/components/ChangelogIndicator.tsx

@@ -0,0 +1,78 @@
+import { useEffect, useState } from "react";
+import { Link, useLocation } from "react-router";
+import { useTranslation } from "react-i18next";
+
+const LAST_SEEN_KEY = "changelog:lastSeen";
+const DISABLED_KEY = "changelog:disabled";
+
+export function ChangelogLink({
+  newestDate,
+  className,
+}: {
+  newestDate: string | null;
+  className: (active: boolean) => string;
+}) {
+  const { t } = useTranslation("journal");
+  const location = useLocation();
+  const [showDot, setShowDot] = useState(false);
+  const isActive =
+    location.pathname === "/changelog" ||
+    location.pathname.startsWith("/changelog/");
+
+  useEffect(() => {
+    if (!newestDate) return;
+    const disabled = localStorage.getItem(DISABLED_KEY);
+    if (disabled === "true") return;
+    const lastSeen = localStorage.getItem(LAST_SEEN_KEY);
+    if (!lastSeen || newestDate > lastSeen) {
+      setShowDot(true);
+    }
+  }, [newestDate]);
+
+  useEffect(() => {
+    if (isActive && newestDate) {
+      localStorage.setItem(LAST_SEEN_KEY, newestDate);
+      setShowDot(false);
+    }
+  }, [isActive, newestDate]);
+
+  return (
+    <Link to="/changelog" className={className(isActive)}>
+      {t("nav.changelog")}
+      {showDot && (
+        <span className="ml-1 inline-block h-2 w-2 rounded-full bg-blue-500" />
+      )}
+    </Link>
+  );
+}
+
+export function ChangelogNotificationToggle() {
+  const { t } = useTranslation("journal");
+  const [disabled, setDisabled] = useState(false);
+
+  useEffect(() => {
+    setDisabled(localStorage.getItem(DISABLED_KEY) === "true");
+  }, []);
+
+  function toggle() {
+    if (disabled) {
+      localStorage.removeItem(DISABLED_KEY);
+      setDisabled(false);
+    } else {
+      localStorage.setItem(DISABLED_KEY, "true");
+      setDisabled(true);
+    }
+  }
+
+  return (
+    <label className="flex cursor-pointer items-center gap-2 text-sm text-gray-500">
+      <input
+        type="checkbox"
+        checked={!disabled}
+        onChange={toggle}
+        className="rounded border-gray-300"
+      />
+      {t("changelog.showNotifications")}
+    </label>
+  );
+}