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/(chapter)/groups/GroupsTabs.tsx

@@ -0,0 +1,28 @@
+'use client';
+import Link from 'next/link';
+
+interface Props {
+  current: 'mine' | 'shared' | 'all';
+  counts: { mine: number; shared: number };
+}
+
+export function GroupsTabs({ current, counts }: Props) {
+  const tabs: { key: Props['current']; label: string; href: string }[] = [
+    { key: 'mine', label: `My Groups (${counts.mine})`, href: '/groups' },
+    { key: 'shared', label: `Shared with me (${counts.shared})`, href: '/groups?tab=shared' },
+  ];
+  return (
+    <div className="flex border-b border-gray-200">
+      {tabs.map((t) => (
+        <Link key={t.key} href={t.href}
+          className={`px-4 py-2 text-sm border-b-2 -mb-px transition-colors ${
+            current === t.key
+              ? 'border-blue-600 text-blue-700 font-medium'
+              : 'border-transparent text-gray-600 hover:text-gray-900'
+          }`}>
+          {t.label}
+        </Link>
+      ))}
+    </div>
+  );
+}