feat: 支持加载进度提示和 API 重试机制

- 添加 ProgressTips 节点到 PageLoading 展示加载状态消息
- 连接 statusLabel 到 ProgressTips 组件
- LevelDataManager 添加 API 请求重试机制（重试 2 次）
- 优化进度消息：正在请求服务端数据、正在加载游戏必备资源等
- 初始化失败时显示"网络异常，请重新打开游戏"

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/PageLoading.prefab

@@ -23,22 +23,25 @@
       },
       {
         "__id__": 10
+      },
+      {
+        "__id__": 24
       }
     ],
     "_active": true,
     "_components": [
       {
-        "__id__": 24
+        "__id__": 30
       },
       {
-        "__id__": 26
+        "__id__": 32
       },
       {
-        "__id__": 28
+        "__id__": 34
       }
     ],
     "_prefab": {
-      "__id__": 30
+      "__id__": 36
     },
     "_lpos": {
       "__type__": "cc.Vec3",
@@ -530,6 +533,165 @@
     "targetOverrides": null,
     "nestedPrefabInstanceRoots": null
   },
+  {
+    "__type__": "cc.Node",
+    "_name": "ProgressTips",
+    "_objFlags": 0,
+    "__editorExtras__": {},
+    "_parent": {
+      "__id__": 1
+    },
+    "_children": [],
+    "_active": true,
+    "_components": [
+      {
+        "__id__": 25
+      },
+      {
+        "__id__": 27
+      }
+    ],
+    "_prefab": {
+      "__id__": 29
+    },
+    "_lpos": {
+      "__type__": "cc.Vec3",
+      "x": -10.607,
+      "y": -622.285,
+      "z": 0
+    },
+    "_lrot": {
+      "__type__": "cc.Quat",
+      "x": 0,
+      "y": 0,
+      "z": 0,
+      "w": 1
+    },
+    "_lscale": {
+      "__type__": "cc.Vec3",
+      "x": 1,
+      "y": 1,
+      "z": 1
+    },
+    "_mobility": 0,
+    "_layer": 1073741824,
+    "_euler": {
+      "__type__": "cc.Vec3",
+      "x": 0,
+      "y": 0,
+      "z": 0
+    },
+    "_id": ""
+  },
+  {
+    "__type__": "cc.UITransform",
+    "_name": "",
+    "_objFlags": 0,
+    "__editorExtras__": {},
+    "node": {
+      "__id__": 24
+    },
+    "_enabled": true,
+    "__prefab": {
+      "__id__": 26
+    },
+    "_contentSize": {
+      "__type__": "cc.Size",
+      "width": 80,
+      "height": 50.4
+    },
+    "_anchorPoint": {
+      "__type__": "cc.Vec2",
+      "x": 0.5,
+      "y": 0.5
+    },
+    "_id": ""
+  },
+  {
+    "__type__": "cc.CompPrefabInfo",
+    "fileId": "6eZWHqpJtCTpZ/0qF30Pdo"
+  },
+  {
+    "__type__": "cc.Label",
+    "_name": "",
+    "_objFlags": 0,
+    "__editorExtras__": {},
+    "node": {
+      "__id__": 24
+    },
+    "_enabled": true,
+    "__prefab": {
+      "__id__": 28
+    },
+    "_customMaterial": null,
+    "_srcBlendFactor": 2,
+    "_dstBlendFactor": 4,
+    "_color": {
+      "__type__": "cc.Color",
+      "r": 255,
+      "g": 255,
+      "b": 255,
+      "a": 255
+    },
+    "_string": "进度",
+    "_horizontalAlign": 1,
+    "_verticalAlign": 1,
+    "_actualFontSize": 40,
+    "_fontSize": 40,
+    "_fontFamily": "Arial",
+    "_lineHeight": 40,
+    "_overflow": 0,
+    "_enableWrapText": true,
+    "_font": null,
+    "_isSystemFontUsed": true,
+    "_spacingX": 0,
+    "_isItalic": false,
+    "_isBold": false,
+    "_isUnderline": false,
+    "_underlineHeight": 2,
+    "_cacheMode": 0,
+    "_enableOutline": false,
+    "_outlineColor": {
+      "__type__": "cc.Color",
+      "r": 0,
+      "g": 0,
+      "b": 0,
+      "a": 255
+    },
+    "_outlineWidth": 2,
+    "_enableShadow": false,
+    "_shadowColor": {
+      "__type__": "cc.Color",
+      "r": 0,
+      "g": 0,
+      "b": 0,
+      "a": 255
+    },
+    "_shadowOffset": {
+      "__type__": "cc.Vec2",
+      "x": 2,
+      "y": 2
+    },
+    "_shadowBlur": 2,
+    "_id": ""
+  },
+  {
+    "__type__": "cc.CompPrefabInfo",
+    "fileId": "e1paQuq1lB8bP8W2opCL2A"
+  },
+  {
+    "__type__": "cc.PrefabInfo",
+    "root": {
+      "__id__": 1
+    },
+    "asset": {
+      "__id__": 0
+    },
+    "fileId": "f1spDHT01G1LKPBUMVSzhP",
+    "instance": null,
+    "targetOverrides": null,
+    "nestedPrefabInstanceRoots": null
+  },
   {
     "__type__": "cc.UITransform",
     "_name": "",
@@ -540,7 +702,7 @@
     },
     "_enabled": true,
     "__prefab": {
-      "__id__": 25
+      "__id__": 31
     },
     "_contentSize": {
       "__type__": "cc.Size",
@@ -568,11 +730,14 @@
     },
     "_enabled": true,
     "__prefab": {
-      "__id__": 27
+      "__id__": 33
     },
     "progressBar": {
       "__id__": 21
     },
+    "statusLabel": {
+      "__id__": 27
+    },
     "_id": ""
   },
   {
@@ -589,7 +754,7 @@
     },
     "_enabled": true,
     "__prefab": {
-      "__id__": 29
+      "__id__": 35
     },
     "_alignFlags": 45,
     "_target": null,