feat: harden auth and study workflows

- replace plaintext login and unlock requests with RSA-OAEP/AES-GCM encrypted payloads

- add login challenge replay protection, production RSA key validation, and auth tests

- wire compose to environment-driven dev/prod settings without committing local secrets

- update setup-config smoke scripts and Postman docs for encrypted login

- add visit schedule migrations/tests and update study/subject setup workflows

frontend/src/utils/loginCrypto.ts

@@ -0,0 +1,56 @@
+const pemToArrayBuffer = (pem: string): ArrayBuffer => {
+  const base64 = pem
+    .replace(/-----BEGIN PUBLIC KEY-----/g, "")
+    .replace(/-----END PUBLIC KEY-----/g, "")
+    .replace(/\s/g, "");
+  const binary = atob(base64);
+  const bytes = new Uint8Array(binary.length);
+  for (let index = 0; index < binary.length; index += 1) {
+    bytes[index] = binary.charCodeAt(index);
+  }
+  return bytes.buffer;
+};
+
+const arrayBufferToBase64 = (buffer: ArrayBuffer): string => {
+  const bytes = new Uint8Array(buffer);
+  let binary = "";
+  bytes.forEach((byte) => {
+    binary += String.fromCharCode(byte);
+  });
+  return btoa(binary);
+};
+
+const assertSecureCryptoAvailable = () => {
+  if (!window.isSecureContext || !crypto?.subtle) {
+    throw new Error("当前浏览器环境不支持安全登录加密，请使用 HTTPS 或 localhost 访问系统");
+  }
+};
+
+export const encryptLoginPayload = async (
+  publicKeyPem: string,
+  payload: { email: string; password: string; challenge: string }
+): Promise<string> => {
+  assertSecureCryptoAvailable();
+  const publicKey = await crypto.subtle.importKey(
+    "spki",
+    pemToArrayBuffer(publicKeyPem),
+    {
+      name: "RSA-OAEP",
+      hash: "SHA-256",
+    },
+    false,
+    ["encrypt"]
+  );
+  const aesKey = await crypto.subtle.generateKey({ name: "AES-GCM", length: 256 }, true, ["encrypt"]);
+  const iv = crypto.getRandomValues(new Uint8Array(12));
+  const encoded = new TextEncoder().encode(JSON.stringify(payload));
+  const encryptedData = await crypto.subtle.encrypt({ name: "AES-GCM", iv }, aesKey, encoded);
+  const rawAesKey = await crypto.subtle.exportKey("raw", aesKey);
+  const encryptedKey = await crypto.subtle.encrypt({ name: "RSA-OAEP" }, publicKey, rawAesKey);
+  const envelope = {
+    encrypted_key: arrayBufferToBase64(encryptedKey),
+    iv: arrayBufferToBase64(iv.buffer),
+    data: arrayBufferToBase64(encryptedData),
+  };
+  return btoa(JSON.stringify(envelope));
+};