Fix TabBar icon assets and simplify Podfile post_install.

Rename tab icons to snake_case with @2x/@3x scales, register CYL plus button at app launch, and remove redundant Podfile hooks already covered by the Xcode project.

Co-authored-by: Cursor <cursoragent@cursor.com>

suixinkan_ios/Assets.xcassets/tab_order_selected.imageset/Contents.json

@@ -0,0 +1,23 @@
+{
+  "images" : [
+    {
+      "filename" : "tab_order_selected.png",
+      "idiom" : "universal",
+      "scale" : "1x"
+    },
+    {
+      "filename" : "tab_order_selected@2x.png",
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "filename" : "tab_order_selected@3x.png",
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}