ADDED - Admin SEO page, robots/sitemap hardening and media/maintenance security fixes

SEO
- New Settings > SEO admin page (seo_settings in app_config): indexing switch,
  Google/Bing verification, X handle, JSON-LD identity (Person/Organization,
  sameAs), per-locale keywords, readiness checklist and open links for
  sitemap.xml / robots.txt / manifest.
- robots.txt is now dynamic: disallows admin, api, success and coming-soon
  paths; blocks everything while indexing is off or maintenance is on.
- sitemap.xml carries hreflang alternates per URL, lists only categories with
  published projects, and is empty while hidden.
- Metadata: robots + verification meta, og:locale in de_DE/en_US/ar_AR form,
  alternateLocale, twitter site/creator, project cover as OG image with
  article type, noindex on /success and /coming-soon.
- JSON-LD: WebSite + publisher graph on all public pages, CreativeWork per
  project (view-mode independent).

Security
- Maintenance bypass now requires a correctly signed admin cookie; the
  middleware previously only checked the cookie existed. Token helpers moved
  to lib/admin-session-token.ts (shared by proxy.ts and lib/admin-auth.ts).
- Media uploads: magic-byte validation against the declared type, SVG
  sanitization (script/handlers/foreignObject/javascript: rejected), upload
  folder sanitized, kind inferred from the real file.
- Media route: fixed prefix-based path check that accepted sibling
  directories, unknown extensions return 404, nosniff header, CSP sandbox on
  SVG, gif content type added.
- External media URLs: protocol-relative (//host) URLs rejected.

Portfolio
- Project and category slugs share /portfolio/[slug]; saving now rejects a
  slug already used on the other side instead of silently shadowing it.

Tooling/docs
- Lint: ignore scripts/legacy-prisma-seed.cjs, drop unused import.
- New docs/SEO.md; FEATURES, ARCHITECTURE (Drizzle instead of Prisma), admin
  spec and CLAUDE.md updated.
- Tests for all of the above (unit + integration); suite green.

tests/integration/actions-site-settings.test.ts

@@ -11,10 +11,11 @@ vi.mock("@/lib/admin-auth", async () => {
 });
 
 import {
+  saveSeoSettingsAction,
   saveSiteBrandSettingsAction,
   saveSiteLocalizationSettingsAction,
 } from "@/app/_admin/site-settings/actions";
-import { getSiteSettings, getSiteSettingsMediaBindings } from "@/lib/app-config";
+import { getSeoSettings, getSiteSettings, getSiteSettingsMediaBindings } from "@/lib/app-config";
 import { adminAuth, captureRedirect, formDataFrom, resetNextMocks } from "@/tests/helpers/next-mocks";
 
 beforeEach(() => {
@@ -102,3 +103,51 @@ describe("saveSiteLocalizationSettingsAction", () => {
     expect(url).toBe("/");
   });
 });
+
+describe("saveSeoSettingsAction", () => {
+  it("persists normalized seo settings", async () => {
+    const url = await captureRedirect(() =>
+      saveSeoSettingsAction(
+        formDataFrom({
+          allowIndexing: "on",
+          googleSiteVerification: "g-1",
+          twitterHandle: "moh",
+          structuredDataType: "Organization",
+          structuredDataName: "Studio",
+          sameAs: "https://a.com\nhttps://b.com",
+          keywordsDe: "a, b",
+        }),
+      ),
+    );
+    expect(url).toContain("success=");
+    const seo = await getSeoSettings();
+    expect(seo).toMatchObject({
+      allowIndexing: true,
+      googleSiteVerification: "g-1",
+      twitterHandle: "@moh",
+      structuredDataType: "Organization",
+      sameAs: ["https://a.com", "https://b.com"],
+    });
+    expect(seo.locales.de.keywords).toBe("a, b");
+  });
+
+  it("turns indexing off when the checkbox is missing", async () => {
+    await captureRedirect(() => saveSeoSettingsAction(formDataFrom({})));
+    expect((await getSeoSettings()).allowIndexing).toBe(false);
+  });
+
+  it("rejects an invalid verification token without saving", async () => {
+    await captureRedirect(() => saveSeoSettingsAction(formDataFrom({ allowIndexing: "on", googleSiteVerification: "ok" })));
+    const url = await captureRedirect(() =>
+      saveSeoSettingsAction(formDataFrom({ allowIndexing: "on", googleSiteVerification: "<bad>" })),
+    );
+    expect(url).toContain("error=");
+    expect((await getSeoSettings()).googleSiteVerification).toBe("ok");
+  });
+
+  it("redirects unauthenticated users", async () => {
+    adminAuth.authenticated = false;
+    const url = await captureRedirect(() => saveSeoSettingsAction(formDataFrom({})));
+    expect(url).not.toContain("success=");
+  });
+});