feat(ios): refine adaptive theme and unified controls

apps/ios/Sources/MultiSimAdmin/Features/Fleet/InstanceFormView.swift

@@ -39,17 +39,13 @@ struct InstanceFormView: View {
             .aiBottomActionBar {
                 HStack(spacing: 10) {
                     Button("取消") { dismiss() }
-                        .buttonStyle(
-                            AIButtonStyle(
-                                kind: .secondary,
-                                size: .regular,
-                                fixedWidth: AITheme.footerSecondaryButtonWidth
-                            )
-                        )
+                        .buttonStyle(AIButtonStyle(kind: .secondary, size: .regular, fillsWidth: true))
+                        .frame(maxWidth: .infinity)
 
                     Button("保存实例") { save() }
                         .buttonStyle(AIButtonStyle(kind: .primary, size: .regular, fillsWidth: true))
                         .disabled(!canSave)
+                        .frame(maxWidth: .infinity)
                 }
             }
         }
@@ -62,9 +58,7 @@ struct InstanceFormView: View {
         secure: Bool = false
     ) -> some View {
         VStack(alignment: .leading, spacing: 6) {
-            Text(title)
-                .font(.subheadline.weight(.semibold))
-                .foregroundStyle(AITheme.ink)
+            AIFieldLabel(title)
             if secure {
                 SecureField(placeholder, text: text)
                     .textFieldStyle(AIFieldStyle())