feat: isolate all four portals with route groups + polished design system

Fix blank /org/login (and /admin/login): the guarded portal layout was
wrapping its own login route, rendering null when unauthenticated. Move
each portal's authed pages into a (authed)/(chapter) route group so login
pages live outside the guard.

Structure:
- app/(chapter)/* — chapter admin pages + guarded layout (was root-level)
- app/org/(authed)/* — org pages + guarded layout; /org/login now free
- app/admin/(authed)/* — admin pages + guarded layout; /admin/login free
- Root layout slimmed to providers only (no shared sidebar)
- Convert moved files' relative imports to @/app alias

Design system:
- PortalShell: shared sidebar shell (brand mark, themed active nav with
  accent bar, avatar dropdown user menu, loading skeletons)
- portal-theme.ts: per-portal theme tokens (violet/slate/blue/emerald)
- PortalLoginShell redesigned: two-column with gradient branding panel,
  dotted pattern, value-prop highlights, built-in back link
- New shadcn components: Avatar, DropdownMenu, Skeleton
- Move shared DraftCard to _components/draft-card.tsx (used by 2 portals)
- Portal selector: remove Super Admin card, icon tiles, hover lift
- All 4 login pages use react-hook-form + Zod + themed shell
- Member nav restored to full 11-section list with icons

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/app/_components/portal-login-shell.tsx

@@ -1,47 +1,83 @@
+import Link from 'next/link';
 import { cn } from '../_lib/utils';
+import { PORTAL_THEMES, type PortalTheme } from './portal-theme';
+import { Check, ArrowLeft } from 'lucide-react';
 
 interface PortalLoginShellProps {
   title: string;
   subtitle: string;
-  accentClass?: string;
+  theme: PortalTheme;
+  /** Short value-prop bullets shown on the branding panel */
+  highlights?: string[];
   children: React.ReactNode;
   footer?: React.ReactNode;
 }
 
-export function PortalLoginShell({ title, subtitle, accentClass = 'bg-primary', children, footer }: PortalLoginShellProps) {
+export function PortalLoginShell({ title, subtitle, theme, highlights = [], children, footer }: PortalLoginShellProps) {
+  const t = PORTAL_THEMES[theme];
+
   return (
     <div className="min-h-screen grid lg:grid-cols-2">
-      {/* Left branding panel */}
-      <div className={cn('hidden lg:flex flex-col justify-between p-10 text-white', accentClass)}>
-        <div className="flex items-center gap-2">
-          <span className="font-bold text-xl tracking-tight">TOWER</span>
+      {/* Branding panel */}
+      <div className={cn('relative hidden lg:flex flex-col justify-between p-12 text-white overflow-hidden', t.gradient)}>
+        {/* decorative pattern */}
+        <div
+          className="absolute inset-0 opacity-10"
+          style={{
+            backgroundImage: 'radial-gradient(circle at 1px 1px, white 1px, transparent 0)',
+            backgroundSize: '24px 24px',
+          }}
+        />
+        <div className="relative flex items-center gap-3">
+          <div className="size-9 rounded-xl bg-white/15 backdrop-blur flex items-center justify-center font-bold">T</div>
+          <span className="font-semibold text-lg tracking-tight">TOWER</span>
         </div>
-        <div>
-          <blockquote className="space-y-2">
-            <p className="text-lg font-medium leading-relaxed">
-              "Community knowledge, beautifully organised."
-            </p>
-            <footer className="text-sm opacity-70">Insignia TOWER Platform</footer>
-          </blockquote>
+
+        <div className="relative space-y-6">
+          <h2 className="text-3xl font-bold leading-tight max-w-sm">{title}</h2>
+          {highlights.length > 0 && (
+            <ul className="space-y-3">
+              {highlights.map((h) => (
+                <li key={h} className="flex items-center gap-3 text-sm text-white/90">
+                  <span className="size-5 rounded-full bg-white/15 flex items-center justify-center shrink-0">
+                    <Check className="size-3" />
+                  </span>
+                  {h}
+                </li>
+              ))}
+            </ul>
+          )}
         </div>
+
+        <p className="relative text-sm text-white/60">Community Knowledge Infrastructure Platform</p>
       </div>
 
-      {/* Right form panel */}
-      <div className="flex items-center justify-center p-8 bg-background">
-        <div className="w-full max-w-sm space-y-6">
+      {/* Form panel */}
+      <div className="flex items-center justify-center p-6 sm:p-8 bg-background">
+        <div className="w-full max-w-sm space-y-8">
           {/* Mobile logo */}
           <div className="flex items-center gap-2 lg:hidden">
-            <span className="font-bold text-lg">TOWER</span>
+            <div className={cn('size-8 rounded-lg flex items-center justify-center text-white font-bold text-sm', t.gradient)}>T</div>
+            <span className="font-semibold">TOWER</span>
           </div>
 
-          <div className="space-y-1">
+          <div className="space-y-2">
             <h1 className="text-2xl font-bold tracking-tight">{title}</h1>
             <p className="text-sm text-muted-foreground">{subtitle}</p>
           </div>
 
           {children}
 
-          {footer && <div className="text-center text-sm text-muted-foreground">{footer}</div>}
+          <div className="space-y-3 text-center">
+            {footer}
+            <Link
+              href="/"
+              className="inline-flex items-center gap-1.5 text-xs text-muted-foreground hover:text-foreground transition-colors"
+            >
+              <ArrowLeft className="size-3" />
+              Back to portal selector
+            </Link>
+          </div>
         </div>
       </div>
     </div>