Add legal pages, ToS acceptance, and alpha banner

- Journal: Impressum (§5 TMG), Terms of Service, GDPR privacy page
- Registration flow: required ToS checkbox, termsAcceptedAt persisted
- Alpha banner on Journal (always visible); alpha badge on Planner hero
- Footer with legal links + GitHub on both apps
- Reduce PII: sendDefaultPii=false, Sentry init only after login (Journal)
- Drop Sentry from Planner (no login, no consent possible)
- Drop localStorage caching from i18n client detection
- Sync SSR i18n resources each request so locale edits HMR without restart

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/journal/app/components/AlphaBanner.tsx

@@ -0,0 +1,10 @@
+import { useTranslation } from "react-i18next";
+
+export function AlphaBanner() {
+  const { t } = useTranslation("journal");
+  return (
+    <div className="bg-amber-50 border-b border-amber-200 px-4 py-2 text-sm text-amber-900">
+      <p>{t("alpha.message")}</p>
+    </div>
+  );
+}

apps/journal/app/components/Footer.tsx

@@ -0,0 +1,33 @@
+import { useTranslation } from "react-i18next";
+
+export function Footer() {
+  const { t } = useTranslation("journal");
+  return (
+    <footer className="mt-16 border-t border-gray-200 bg-white">
+      <div className="mx-auto max-w-7xl px-4 py-6 text-sm text-gray-500">
+        <nav className="flex flex-wrap items-center gap-x-6 gap-y-2">
+          <a href="/legal/imprint" className="hover:text-gray-700">
+            {t("footer.imprint")}
+          </a>
+          <a href="/legal/privacy" className="hover:text-gray-700">
+            {t("footer.privacy")}
+          </a>
+          <a href="/legal/terms" className="hover:text-gray-700">
+            {t("footer.terms")}
+          </a>
+          <a
+            href="https://github.com/trails-cool/trails"
+            className="hover:text-gray-700"
+            target="_blank"
+            rel="noopener noreferrer"
+          >
+            {t("footer.source")}
+          </a>
+          <span className="ml-auto text-xs text-gray-400">
+            {t("footer.alpha")}
+          </span>
+        </nav>
+      </div>
+    </footer>
+  );
+}