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_iosTests/MainScanPlusButtonTests.swift

@@ -41,6 +41,21 @@ final class MainScanPlusButtonTests: XCTestCase {
             )
         }
     }
+
+    /// 测试各 Tab 的图标资源可被加载并挂载到 tabBarItem。
+    func testMainTabBarControllerTabBarItemsHaveImages() {
+        let services = AppServices(apiClient: APIClient(session: MainTabRecordingURLSession()))
+        let controller = MainTabBarController(services: services)
+        controller.loadViewIfNeeded()
+
+        for tab in AppTab.allCases {
+            let item = controller.navigationController(for: tab)?.tabBarItem
+            XCTAssertNotNil(item?.image, "tab \(tab.rawValue) image should not be nil")
+            XCTAssertNotNil(item?.selectedImage, "tab \(tab.rawValue) selectedImage should not be nil")
+            XCTAssertGreaterThan(item?.image?.size.width ?? 0, 0)
+            XCTAssertGreaterThan(item?.selectedImage?.size.width ?? 0, 0)
+        }
+    }
 }
 
 /// 主 Tab 测试使用的空网络会话，确保容器加载不触发真实请求。