feat: 添加用户登录和法律协议页面

- 新增登录页面，支持 Apple 登录和游客登录功能
- 添加用户协议和隐私政策页面，用户需同意后才能登录
- 更新首页逻辑，首次进入时自动跳转到登录页面
- 修改个人信息页面，移除单位选择功能，统一使用 kg 和 cm
- 更新依赖，添加 expo-apple-authentication 库以支持 Apple 登录
- 更新布局以适应新功能的展示和交互

package-lock.json

@@ -15,6 +15,7 @@
         "@react-navigation/native": "^7.1.6",
         "dayjs": "^1.11.13",
         "expo": "~53.0.20",
+        "expo-apple-authentication": "6.4.2",
         "expo-blur": "~14.1.5",
         "expo-constants": "~17.1.7",
         "expo-font": "~13.3.2",
@@ -6329,6 +6330,15 @@
         }
       }
     },
+    "node_modules/expo-apple-authentication": {
+      "version": "6.4.2",
+      "resolved": "https://mirrors.tencent.com/npm/expo-apple-authentication/-/expo-apple-authentication-6.4.2.tgz",
+      "integrity": "sha512-X4u1n3Ql1hOpztXHbKNq4I1l4+Ff82gC6RmEeW43Eht7VE6E8PrQBpYKw+JJv8osrCJt7R5O1PZwed6WLN5oig==",
+      "license": "MIT",
+      "peerDependencies": {
+        "expo": "*"
+      }
+    },
     "node_modules/expo-asset": {
       "version": "11.1.7",
       "resolved": "https://registry.npmjs.org/expo-asset/-/expo-asset-11.1.7.tgz",