feat: complete remaining Go backend modules

tests/admin-http-auth-compat.test.ts

@@ -0,0 +1,12 @@
+import { readFile } from "node:fs/promises";
+import { describe, expect, it } from "vitest";
+
+describe("Go legacy auth compatibility HTTP v1 contract", () => {
+  it("pins login, callback, and disabled captcha endpoints", async () => {
+    const fixture = JSON.parse(await readFile(new URL("../contracts/admin/http-auth-compat-v1.json", import.meta.url), "utf8"));
+    const source = await readFile(new URL("../backend/internal/httpapi/auth_compat.go", import.meta.url), "utf8");
+    expect(fixture.routes.map((route: { path: string }) => route.path)).toEqual(["/api/auth/login", "/api/auth/callback", "/api/auth/captcha"]);
+    expect(source).toContain("callback_failed");
+    expect(source).toContain("平台账号登录不使用外部验证码。");
+  });
+});