fix(portal): full-screen overlay + redirect portal-only users

Portal layout: removed conflicting (portal)/layout.tsx that had
duplicate html/body tags. Portal page now uses fixed overlay
(z-[100]) that covers the entire screen including sidebar.

Middleware: portal-only users (dan.tiurbe) are automatically
redirected from any non-portal route to /portal. They can still
access /api/ and /auth/ routes normally.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/app/(portal)/portal/page.tsx

@@ -1477,7 +1477,7 @@ function HartaContent() {
 
 export default function PortalPage() {
   return (
-    <div className="min-h-screen flex flex-col">
+    <div className="fixed inset-0 z-[100] bg-background overflow-auto flex flex-col">
       {/* Header */}
       <Tabs defaultValue="rgi" className="flex-1 flex flex-col gap-0">
         <header className="border-b bg-background/95 backdrop-blur-sm px-4 py-2 flex items-center gap-4 shrink-0">