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.

app/_admin/site-settings/actions.ts

@@ -12,7 +12,9 @@ import {
   SITE_SETTINGS_FAVICON_FIELD_KEY,
   SITE_SETTINGS_LOGO_DARK_FIELD_KEY,
   SITE_SETTINGS_LOGO_LIGHT_FIELD_KEY,
+  getSeoSettings,
   getSiteSettings,
+  updateSeoSettings,
   updateSiteSettings,
 } from "@/lib/app-config";
 import { getAdminAppPath, toInternalAdminPath } from "@/lib/admin-routing";
@@ -24,6 +26,15 @@ import {
   type SiteSettings,
 } from "@/lib/site-settings";
 import { clearAdminSessionCookie, isAdminAuthenticated } from "@/lib/admin-auth";
+import {
+  normalizeKeywords,
+  normalizeSameAs,
+  normalizeStructuredDataType,
+  normalizeTwitterHandle,
+  normalizeVerificationToken,
+  type SeoSettings,
+} from "@/lib/seo-settings";
+import { isCheckedFormValue } from "@/lib/form-data";
 import { replaceEntityMediaUsages } from "@/lib/media";
 import { resolveMediaSelection } from "@/lib/media-service";
 import { routing } from "@/i18n/routing";
@@ -329,3 +340,63 @@ export async function saveSiteLocalizationSettingsAction(formData: FormData) {
     redirect(withFlash(getAdminAppPath("/site-settings/localization"), { error: message }));
   }
 }
+
+export async function saveSeoSettingsAction(formData: FormData) {
+  await ensureAdmin();
+
+  try {
+    const currentSettings = await getSeoSettings();
+    const googleRaw = String(formData.get("googleSiteVerification") ?? "").trim();
+    const bingRaw = String(formData.get("bingSiteVerification") ?? "").trim();
+    const twitterRaw = String(formData.get("twitterHandle") ?? "").trim();
+    const googleSiteVerification = normalizeVerificationToken(googleRaw);
+    const bingSiteVerification = normalizeVerificationToken(bingRaw);
+    const twitterHandle = normalizeTwitterHandle(twitterRaw);
+
+    if (googleRaw && !googleSiteVerification) {
+      throw new Error("Google Verification Code darf nur Buchstaben, Zahlen, - und _ enthalten.");
+    }
+
+    if (bingRaw && !bingSiteVerification) {
+      throw new Error("Bing Verification Code darf nur Buchstaben, Zahlen, - und _ enthalten.");
+    }
+
+    if (twitterRaw && !twitterHandle) {
+      throw new Error("X/Twitter Handle ist ungueltig (max. 15 Zeichen, Buchstaben/Zahlen/_).");
+    }
+
+    const parsedSettings: SeoSettings = {
+      ...currentSettings,
+      allowIndexing: isCheckedFormValue(formData.get("allowIndexing")),
+      googleSiteVerification,
+      bingSiteVerification,
+      twitterHandle,
+      structuredDataType: normalizeStructuredDataType(formData.get("structuredDataType")),
+      structuredDataName: String(formData.get("structuredDataName") ?? "").trim().slice(0, 120),
+      structuredDataJobTitle: String(formData.get("structuredDataJobTitle") ?? "").trim().slice(0, 160),
+      sameAs: normalizeSameAs(formData.get("sameAs")),
+      locales: {
+        ar: { keywords: normalizeKeywords(formData.get("keywordsAr")) },
+        en: { keywords: normalizeKeywords(formData.get("keywordsEn")) },
+        de: { keywords: normalizeKeywords(formData.get("keywordsDe")) },
+      },
+    };
+
+    await updateSeoSettings(parsedSettings);
+    const siteSettings = await getSiteSettings();
+    await revalidateSiteSettingsPages(siteSettings.defaultLocale);
+    revalidatePath("/sitemap.xml");
+    revalidatePath("/robots.txt");
+    revalidatePath(toInternalAdminPath("/site-settings/seo"));
+    redirect(withFlash(getAdminAppPath("/site-settings/seo"), { success: "SEO Einstellungen gespeichert." }));
+  } catch (error) {
+    if (isRedirectError(error)) {
+      throw error;
+    }
+
+    const message =
+      error instanceof Error ? error.message : "SEO Einstellungen konnten nicht gespeichert werden.";
+
+    redirect(withFlash(getAdminAppPath("/site-settings/seo"), { error: message }));
+  }
+}