feat: add AI-generated study plan creation dialog and API integration

- Implemented CreatePlanDialog component for generating study plans using AI.
- Integrated postAPI function for handling API requests.
- Updated planes.tsx to include AI plan generation logic.
- Modified usuarios.tsx to enable email confirmation for new users.
- Added Switch component for UI consistency.
- Created api.ts for centralized API handling.
- Developed carreras.tsx for managing career data with filtering and CRUD operations.
- Added CarreraFormDialog and CarreraDetailDialog for creating and editing career details.
- Implemented CriterioFormDialog for adding criteria to careers.

src/lib/api.ts

@@ -0,0 +1,34 @@
+// api.ts
+const API_BASE =
+  (import.meta.env.VITE_API_BASE?.replace(/\/$/, "")) ||
+  "http://localhost:3001"; // 👈 tu Bun.serve real
+
+export async function postAPI<T=any>(path: string, body: any): Promise<T> {
+  const url = `${API_BASE}${path}`;
+  const r = await fetch(url, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    // Si necesitas cookies, agrega: credentials: "include",
+    body: JSON.stringify(body),
+  });
+
+  const ct = r.headers.get("content-type") || "";
+  const isHTML = ct.includes("text/html");
+  const text = await r.text();
+
+  if (!r.ok) {
+    throw new Error(
+      isHTML
+        ? "El servidor respondió HTML (probable 404 del dashboard/puerto 3000). Revisa API_BASE y el puerto."
+        : text
+    );
+  }
+
+  // Si el server devolvió JSON correctamente:
+  if (ct.includes("application/json")) return JSON.parse(text) as T;
+
+  // Último recurso: intenta parsear
+  try { return JSON.parse(text) as T } catch {
+    throw new Error("Respuesta no-JSON desde la API.");
+  }
+}