feat(web): scaffold Next.js 16 dashboard with design system and auth client (#82)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/app/(auth)/login/page.tsx

@@ -0,0 +1,58 @@
+'use client';
+
+import Link from 'next/link';
+
+export default function LoginPage(): React.ReactElement {
+  return (
+    <div>
+      <h1 className="text-2xl font-semibold">Sign in</h1>
+      <p className="mt-1 text-sm text-text-secondary">Sign in to your Mosaic account</p>
+
+      <form className="mt-6 space-y-4" onSubmit={(e) => e.preventDefault()}>
+        <div>
+          <label htmlFor="email" className="block text-sm font-medium text-text-secondary">
+            Email
+          </label>
+          <input
+            id="email"
+            name="email"
+            type="email"
+            autoComplete="email"
+            required
+            className="mt-1 block w-full rounded-lg border border-surface-border bg-surface-elevated px-3 py-2 text-sm text-text-primary placeholder:text-text-muted focus:border-blue-500 focus:outline-none focus:ring-1 focus:ring-blue-500"
+            placeholder="you@example.com"
+          />
+        </div>
+
+        <div>
+          <label htmlFor="password" className="block text-sm font-medium text-text-secondary">
+            Password
+          </label>
+          <input
+            id="password"
+            name="password"
+            type="password"
+            autoComplete="current-password"
+            required
+            className="mt-1 block w-full rounded-lg border border-surface-border bg-surface-elevated px-3 py-2 text-sm text-text-primary placeholder:text-text-muted focus:border-blue-500 focus:outline-none focus:ring-1 focus:ring-blue-500"
+            placeholder="••••••••"
+          />
+        </div>
+
+        <button
+          type="submit"
+          className="w-full rounded-lg bg-blue-600 px-4 py-2.5 text-sm font-medium text-white transition-colors hover:bg-blue-700 focus:outline-none focus:ring-2 focus:ring-blue-500 focus:ring-offset-2 focus:ring-offset-surface-card"
+        >
+          Sign in
+        </button>
+      </form>
+
+      <p className="mt-4 text-center text-sm text-text-muted">
+        Don&apos;t have an account?{' '}
+        <Link href="/register" className="text-blue-400 hover:text-blue-300">
+          Sign up
+        </Link>
+      </p>
+    </div>
+  );
+}