Add jefe mecánico to client booking flow

Cliente now picks a jefe mecánico after choosing the service so the
calendar shows that specific jefe's availability. Each jefe has its own
configurable parallel slot capacity (replacing the global SLOTS_PARALELOS
= 5). Admins manage jefes from /admin/jefes; jefes log in to /jefe to
see their daily agenda.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/app/jefe/page.tsx

@@ -0,0 +1,51 @@
+"use client";
+import { useState } from "react";
+import { useRouter } from "next/navigation";
+import Button from "@/components/ui/Button";
+import Input from "@/components/ui/Input";
+import Card from "@/components/ui/Card";
+
+export default function JefeLoginPage() {
+  const router = useRouter();
+  const [form, setForm] = useState({ email: "", password: "" });
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState("");
+
+  function set(f: string) {
+    return (e: React.ChangeEvent<HTMLInputElement>) =>
+      setForm((v) => ({ ...v, [f]: e.target.value }));
+  }
+
+  async function handleSubmit(e: React.FormEvent) {
+    e.preventDefault();
+    setLoading(true);
+    setError("");
+    const res = await fetch("/api/auth/jefe-login", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(form),
+    });
+    const data = await res.json();
+    setLoading(false);
+    if (!res.ok) { setError(data.error || "Credenciales incorrectas"); return; }
+    router.push("/jefe/dashboard");
+  }
+
+  return (
+    <div className="flex flex-col items-center justify-center min-h-screen">
+      <Card className="w-full max-w-sm mx-4">
+        <div className="text-center mb-6">
+          <div className="text-4xl mb-2">🔧</div>
+          <h1 className="text-xl font-bold text-gray-800">Agenda del jefe mecánico</h1>
+          <p className="text-sm text-gray-500 mt-1">Ingresá con tus credenciales</p>
+        </div>
+        <form onSubmit={handleSubmit} className="flex flex-col gap-4">
+          <Input id="email" type="email" label="Email" placeholder="jefe@taller.com" value={form.email} onChange={set("email")} required />
+          <Input id="password" type="password" label="Contraseña" placeholder="••••••••" value={form.password} onChange={set("password")} required />
+          {error && <p className="text-sm text-red-500 text-center">{error}</p>}
+          <Button type="submit" loading={loading} className="w-full">Ingresar</Button>
+        </form>
+      </Card>
+    </div>
+  );
+}