feat: add user role types and auth middleware

- lib/auth/roles.ts: UserRole union, ALL_ROLES, ROLE_HOME, getRoleHome, isValidRole (pure, no Supabase imports)
- __tests__/lib/auth/roles.test.ts: 8 TDD tests (written before implementation)
- middleware.ts: createServerClient with request.cookies pattern, unauthenticated redirect to /login, role-based redirect on / and /login

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AWxyMibCuGGtSQSqfajDQ7

middleware.ts

@@ -0,0 +1,61 @@
+// middleware.ts
+import { createServerClient } from '@supabase/ssr'
+import { NextResponse, type NextRequest } from 'next/server'
+import { ROLE_HOME, isValidRole, type UserRole } from '@/lib/auth/roles'
+
+export async function middleware(request: NextRequest) {
+  let supabaseResponse = NextResponse.next({ request })
+
+  const supabase = createServerClient(
+    process.env.NEXT_PUBLIC_SUPABASE_URL!,
+    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
+    {
+      cookies: {
+        getAll() {
+          return request.cookies.getAll()
+        },
+        setAll(cookiesToSet) {
+          cookiesToSet.forEach(({ name, value }) => request.cookies.set(name, value))
+          supabaseResponse = NextResponse.next({ request })
+          cookiesToSet.forEach(({ name, value, options }) =>
+            supabaseResponse.cookies.set(name, value, options),
+          )
+        },
+      },
+    },
+  )
+
+  const {
+    data: { user },
+  } = await supabase.auth.getUser()
+
+  const { pathname } = request.nextUrl
+  const isPublicRoute = pathname.startsWith('/login') || pathname.startsWith('/auth')
+
+  // Unauthenticated → force login
+  if (!user && !isPublicRoute) {
+    return NextResponse.redirect(new URL('/login', request.url))
+  }
+
+  // Authenticated + hitting root or login → redirect to role home
+  if (user && (pathname === '/' || pathname === '/login')) {
+    const { data: profile } = await supabase
+      .from('users')
+      .select('role')
+      .eq('id', user.id)
+      .single()
+
+    const role = profile?.role
+    if (isValidRole(role)) {
+      return NextResponse.redirect(new URL(ROLE_HOME[role as UserRole], request.url))
+    }
+  }
+
+  return supabaseResponse
+}
+
+export const config = {
+  matcher: [
+    '/((?!_next/static|_next/image|favicon.ico|.*\\.(?:svg|png|jpg|jpeg|gif|webp)$).*)',
+  ],
+}