build(ios): 移除 CocoaPods 集成，插件统一走 Swift Package Manager

iOS 插件已全部支持 SPM，但工程仍保留 Podfile，每次构建都会提示移除 CocoaPods 集成；
按提示 pod deintegrate、删除 Podfile，并去掉两个 Flutter xcconfig 里对 Pods-Runner 配置的 include。

ios/Flutter/Debug.xcconfig

@@ -1,2 +1 @@
-#include? "Pods/Target Support Files/Pods-Runner/Pods-Runner.debug.xcconfig"
 #include "Generated.xcconfig"

ios/Flutter/Release.xcconfig

@@ -1,2 +1 @@
-#include? "Pods/Target Support Files/Pods-Runner/Pods-Runner.release.xcconfig"
 #include "Generated.xcconfig"

ios/Podfile

@@ -1,43 +0,0 @@
-# Uncomment this line to define a global platform for your project
-# platform :ios, '13.0'
-
-# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
-ENV['COCOAPODS_DISABLE_STATS'] = 'true'
-
-project 'Runner', {
-  'Debug' => :debug,
-  'Profile' => :release,
-  'Release' => :release,
-}
-
-def flutter_root
-  generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'Generated.xcconfig'), __FILE__)
-  unless File.exist?(generated_xcode_build_settings_path)
-    raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure flutter pub get is executed first"
-  end
-
-  File.foreach(generated_xcode_build_settings_path) do |line|
-    matches = line.match(/FLUTTER_ROOT\=(.*)/)
-    return matches[1].strip if matches
-  end
-  raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Generated.xcconfig, then run flutter pub get"
-end
-
-require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)
-
-flutter_ios_podfile_setup
-
-target 'Runner' do
-  use_frameworks!
-
-  flutter_install_all_ios_pods File.dirname(File.realpath(__FILE__))
-  target 'RunnerTests' do
-    inherit! :search_paths
-  end
-end
-
-post_install do |installer|
-  installer.pods_project.targets.each do |target|
-    flutter_additional_ios_build_settings(target)
-  end
-end