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/uploads/media/[...segments]/route.ts

@@ -14,6 +14,7 @@ export const dynamic = "force-dynamic";
 
 const CONTENT_TYPES: Record<string, string> = {
   ".ico": "image/x-icon",
+  ".gif": "image/gif",
   ".jpg": "image/jpeg",
   ".jpeg": "image/jpeg",
   ".png": "image/png",
@@ -30,15 +31,30 @@ export async function GET(_: Request, { params }: MediaFileRouteProps) {
   try {
     const absolutePath = resolveMediaUploadPath(publicPath);
     const fileBuffer = await readFile(absolutePath);
-    const contentType = CONTENT_TYPES[path.extname(absolutePath).toLowerCase()] ?? "application/octet-stream";
+    const extension = path.extname(absolutePath).toLowerCase();
+    const contentType = CONTENT_TYPES[extension];
 
-    return new NextResponse(fileBuffer, {
-      status: 200,
-      headers: {
-        "Content-Type": contentType,
-        "Cache-Control": "public, max-age=31536000, immutable",
-      },
-    });
+    if (!contentType) {
+      return new NextResponse("Not Found", { status: 404 });
+    }
+
+    const headers: Record<string, string> = {
+      "Content-Type": contentType,
+      "Cache-Control": "public, max-age=31536000, immutable",
+      "X-Content-Type-Options": "nosniff",
+    };
+
+    // SVG is an active document type: sandbox it so an uploaded file can never
+    // run script or reach our origin even if it is opened directly.
+    if (extension === ".svg") {
+      headers["Content-Security-Policy"] = "default-src 'none'; style-src 'unsafe-inline'; sandbox";
+    }
+
+    if (extension === ".pdf") {
+      headers["Content-Disposition"] = "inline";
+    }
+
+    return new NextResponse(new Uint8Array(fileBuffer), { status: 200, headers });
   } catch {
     return new NextResponse("Not Found", {
       status: 404,