feat: bootstrap taller-turnos project

Estructura inicial con Next.js 14, PostgreSQL/Prisma 7, autenticación por
magic link (clientes) y JWT (admins), lógica de scheduling con 4 slots
paralelos y API routes completas para cliente y panel admin.

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

src/lib/auth-admin.ts

@@ -0,0 +1,35 @@
+import { cookies } from "next/headers";
+import { SignJWT, jwtVerify } from "jose";
+
+const SECRET = new TextEncoder().encode(process.env.NEXTAUTH_SECRET || "dev-secret");
+const COOKIE = "admin_session";
+
+export async function crearSesionAdmin(adminId: string): Promise<string> {
+  const token = await new SignJWT({ sub: adminId, role: "admin" })
+    .setProtectedHeader({ alg: "HS256" })
+    .setExpirationTime("8h")
+    .sign(SECRET);
+  return token;
+}
+
+export async function crearSesionCliente(clienteId: string): Promise<string> {
+  const token = await new SignJWT({ sub: clienteId, role: "cliente" })
+    .setProtectedHeader({ alg: "HS256" })
+    .setExpirationTime("24h")
+    .sign(SECRET);
+  return token;
+}
+
+export async function verificarSesion(
+  cookieName: string
+): Promise<{ sub: string; role: string } | null> {
+  const cookieStore = await cookies();
+  const token = cookieStore.get(cookieName)?.value;
+  if (!token) return null;
+  try {
+    const { payload } = await jwtVerify(token, SECRET);
+    return payload as { sub: string; role: string };
+  } catch {
+    return null;
+  }
+}