Improve fresh install flow and auth page routing

- Move /setup out of protected (pages) route group so it's accessible
  without auth (fixes fresh install redirect loop)
- Redirect /login → /register when zero users exist
- Add "Get Started" button on landing page for fresh installs
- Hide register button/link when registration is closed
- Add auth redirects: logged-in users on /login or /register → /dashboard
- Convert register page to server component with server-side checks
- Fix animation snap on auth form buttons (transition-all → scoped)
- Update proxy middleware with /login and /register routes

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

proxy.ts

@@ -1,6 +1,8 @@
 import { getSessionCookie } from "better-auth/cookies";
 import { type NextRequest, NextResponse } from "next/server";
 
+const authRoutes = new Set(["/login", "/register"]);
+
 export function proxy(request: NextRequest) {
   const sessionCookie = getSessionCookie(request);
   const { pathname } = request.nextUrl;
@@ -12,7 +14,13 @@ export function proxy(request: NextRequest) {
     return NextResponse.next();
   }
 
-  if (!sessionCookie) {
+  // Logged-in users on auth pages → dashboard
+  if (authRoutes.has(pathname) && sessionCookie) {
+    return NextResponse.redirect(new URL("/dashboard", request.url));
+  }
+
+  // Unauthenticated users on protected pages → login
+  if (!authRoutes.has(pathname) && !sessionCookie) {
     return NextResponse.redirect(new URL("/login", request.url));
   }
 
@@ -22,6 +30,8 @@ export function proxy(request: NextRequest) {
 export const config = {
   matcher: [
     "/",
+    "/login",
+    "/register",
     "/dashboard",
     "/explore",
     "/settings",