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/prisma.ts

@@ -0,0 +1,12 @@
+import { PrismaClient } from "@prisma/client";
+
+const globalForPrisma = globalThis as unknown as { prisma: PrismaClient };
+
+export const prisma =
+  globalForPrisma.prisma ||
+  new PrismaClient({
+    datasourceUrl: process.env.DATABASE_URL,
+    log: process.env.NODE_ENV === "development" ? ["query", "error"] : ["error"],
+  });
+
+if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma;