feat: portal redesign — shadcn/ui, React Query, Zod, isolated portals

Foundation:
- CLAUDE.md with full coding rules (tech stack, patterns, redirect rules)
- Install @tanstack/react-query, zod, react-hook-form, shadcn/ui deps
- CSS variables design system (Tailwind v4 + tw-animate-css)
- Shared components: Button, Input, Label, Card, Badge, Separator, Form
- PortalLoginShell: two-column login layout (branding left, form right)
- PortalNav: shared sidebar nav used by all portals
- ReactQueryProvider in root layout
- api-client.ts: typed fetch wrapper (no raw fetch in components)

Portal isolation:
- Sidebar now returns null for all non-chapter routes; portals own their layout
- Admin layout: auth guard + PortalNav (slate accent)
- Org layout: auth guard + PortalNav (violet accent)
- Member layout: server-side cookie check → MemberNav client component
- Chapter admin sidebar: PortalNav (blue accent)

Login pages (all use react-hook-form + Zod + PortalLoginShell):
- /login → defaults next to /search (was /) — fixes redirect bug
- /admin/login → replaces /admin
- /org/login → replaces /org
- /member-login → two-step phone+OTP with proper form validation

Portal selector (/) redesigned with accent border-left cards

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

apps/web/app/_lib/utils.ts

@@ -0,0 +1,6 @@
+import { clsx, type ClassValue } from 'clsx';
+import { twMerge } from 'tailwind-merge';
+
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs));
+}