feat(legal): public privacy policy, terms, and homepage for OAuth verification

Adds login-free /privacy and /terms pages (rendered outside the authenticated
tree via a pathname switch in main.tsx) carrying the Google API Services Limited
Use disclosure, YouTube ToS / Google Privacy links, and contact + data-deletion
info. The sign-in screen now describes the app and links to both, satisfying
Google's homepage + privacy-policy requirements for the OAuth consent screen.

frontend/src/components/legal/Terms.tsx

@@ -0,0 +1,67 @@
+import LegalLayout, { CONTACT_EMAIL, H2, LegalLink } from "./LegalLayout";
+
+export default function Terms() {
+  return (
+    <LegalLayout title="Terms of Service">
+      <p>
+        Subfeed is a personal, non-commercial project operated by an individual in Hungary. It
+        provides a filterable view of your own YouTube subscriptions. By accessing or using
+        Subfeed, you agree to these Terms. If you do not agree, do not use the service.
+      </p>
+
+      <H2>The service</H2>
+      <p>
+        Subfeed is offered on an invite-only basis, free of charge, and "as is", without
+        warranties of any kind. It is a hobby project: features may change, and the service may
+        be slowed, interrupted, or discontinued at any time without notice.
+      </p>
+
+      <H2>Your account &amp; acceptable use</H2>
+      <p>
+        You sign in with your Google account and may only access Subfeed with an email that has
+        been invited. You agree to use the service lawfully, not to abuse, disrupt, probe, or
+        overload it, and not to attempt to access other users' data. We may suspend or revoke
+        access at our discretion, for example in case of misuse.
+      </p>
+
+      <H2>Third-party services</H2>
+      <p>
+        Subfeed uses YouTube API Services. By using Subfeed you agree to be bound by the{" "}
+        <LegalLink href="https://www.youtube.com/t/terms">YouTube Terms of Service</LegalLink>.
+        Your data is handled as described in our{" "}
+        <a href="/privacy" className="text-accent hover:underline">Privacy Policy</a> and, for
+        Google data, the{" "}
+        <LegalLink href="https://policies.google.com/privacy">Google Privacy Policy</LegalLink>.
+      </p>
+
+      <H2>No warranty &amp; limitation of liability</H2>
+      <p>
+        To the maximum extent permitted by law, the service is provided without warranty, and
+        the operator is not liable for any indirect, incidental, or consequential damages, or
+        for any loss of data, arising from your use of Subfeed. Your sole remedy if you are
+        dissatisfied is to stop using the service and revoke its access to your account.
+      </p>
+
+      <H2>Governing law</H2>
+      <p>
+        These Terms are governed by the laws of Hungary and applicable European Union law,
+        without regard to conflict-of-law rules.
+      </p>
+
+      <H2>Changes</H2>
+      <p>
+        We may update these Terms; the "Last updated" date above reflects the latest version.
+        Continued use after a change constitutes acceptance.
+      </p>
+
+      <H2>Contact</H2>
+      <p>
+        Questions:{" "}
+        <a href={`mailto:${CONTACT_EMAIL}`} className="text-accent hover:underline">
+          {CONTACT_EMAIL}
+        </a>
+        .
+      </p>
+    </LegalLayout>
+  );
+}