feat: implement multi-step background process for user registration

- Add step 1: Open ChatGPT homepage and prepare for signup.
- Add step 2: Handle email submission and ensure the signup entry page is ready.
- Add step 3: Fill in the password using either a custom or generated password.
- Add step 4: Confirm the registration verification page and handle email verification.
- Add step 5: Generate random user details and handle onboarding redirection.
- Add step 6: Manage OAuth login process and handle login verification.
- Add step 7: Retrieve verification code from email and manage retries.
- Add step 8: Handle consent page interactions and manage callback URLs.
- Add step 9: Submit callback information to CPA or SUB2API based on user settings.
- Implement tests to ensure all steps are correctly imported and functional.

background/steps/step5.js

@@ -0,0 +1,69 @@
+(function attachBackgroundStep5(root, factory) {
+  root.MultiPageBackgroundStep5 = factory();
+})(typeof self !== 'undefined' ? self : globalThis, function createBackgroundStep5Module() {
+  function createStep5Executor(deps = {}) {
+    const {
+      addLog,
+      generateRandomBirthday,
+      generateRandomName,
+      getTabId,
+      handleChatgptOnboardingSkip,
+      isRetryableContentScriptTransportError,
+      LOG_PREFIX,
+      sendToContentScript,
+      waitForStep5ChatgptRedirect,
+    } = deps;
+
+    async function executeStep5() {
+      const { firstName, lastName } = generateRandomName();
+      const { year, month, day } = generateRandomBirthday();
+
+      await addLog(`步骤 5：已生成姓名 ${firstName} ${lastName}，生日 ${year}-${month}-${day}`);
+
+      let step5Result = null;
+      let step5TransportError = null;
+
+      try {
+        step5Result = await sendToContentScript('signup-page', {
+          type: 'EXECUTE_STEP',
+          step: 5,
+          source: 'background',
+          payload: { firstName, lastName, year, month, day },
+        });
+      } catch (err) {
+        if (isRetryableContentScriptTransportError(err)) {
+          step5TransportError = err;
+          console.log(LOG_PREFIX, '步骤 5：内容脚本通信中断，正在检查是否跳转到 ChatGPT 引导页...', err?.message);
+        } else {
+          throw err;
+        }
+      }
+
+      if (step5Result?.chatgptOnboarding) {
+        await addLog('步骤 5：检测到 ChatGPT 引导页跳转，正在处理引导页跳过...');
+        await handleChatgptOnboardingSkip();
+        return;
+      }
+
+      if (step5Result?.chatgptHome) {
+        await addLog('步骤 5：检测到已进入 ChatGPT 页面，注册成功。', 'ok');
+        return;
+      }
+
+      if (step5TransportError) {
+        const signupTabId = await getTabId('signup-page');
+        const redirectedTab = await waitForStep5ChatgptRedirect(signupTabId);
+        if (redirectedTab) {
+          await addLog('步骤 5：内容脚本因页面跳转到 ChatGPT 而断开，正在处理引导页跳过...');
+          await handleChatgptOnboardingSkip(redirectedTab.id);
+          return;
+        }
+        throw step5TransportError;
+      }
+    }
+
+    return { executeStep5 };
+  }
+
+  return { createStep5Executor };
+});