feat: integrate iCloud hide my email generation into OAuth flow

- 合并 PR #72 的核心改动：新增 iCloud Hide My Email 生成、alias 管理与成功后自动标记/删除流程
- 本地补充修复：解决与 Cloudflare Temp Email 分支差异的冲突，并补齐合并后的测试常量
- 影响范围：background 邮箱生成与 Step 9 收尾、sidepanel alias 管理 UI、manifest/rules 与新增 iCloud 测试

rules.json

@@ -0,0 +1,50 @@
+[
+  {
+    "id": 1,
+    "priority": 1,
+    "action": {
+      "type": "modifyHeaders",
+      "requestHeaders": [
+        {
+          "header": "Origin",
+          "operation": "set",
+          "value": "https://www.icloud.com"
+        },
+        {
+          "header": "Referer",
+          "operation": "set",
+          "value": "https://www.icloud.com/"
+        }
+      ]
+    },
+    "condition": {
+      "urlFilter": "|https://*.icloud.com/*",
+      "resourceTypes": ["xmlhttprequest"],
+      "excludedInitiatorDomains": ["apple.com", "icloud.com"]
+    }
+  },
+  {
+    "id": 2,
+    "priority": 1,
+    "action": {
+      "type": "modifyHeaders",
+      "requestHeaders": [
+        {
+          "header": "Origin",
+          "operation": "set",
+          "value": "https://www.icloud.com.cn"
+        },
+        {
+          "header": "Referer",
+          "operation": "set",
+          "value": "https://www.icloud.com.cn/"
+        }
+      ]
+    },
+    "condition": {
+      "urlFilter": "|https://*.icloud.com.cn/*",
+      "resourceTypes": ["xmlhttprequest"],
+      "excludedInitiatorDomains": ["apple.com.cn", "icloud.com.cn"]
+    }
+  }
+]