fix(ui): refine narrow layouts and enable tab swipes

ui/flutter/lib/shared/widgets/app_http_header_group.dart

@@ -0,0 +1,43 @@
+import 'package:flutter/widgets.dart';
+
+import '../../l10n/l10n.dart';
+import '../theme/app_design_tokens.dart';
+import '../theme/app_palette.dart';
+
+/// A single editable name/value pair in a narrow headers form.
+class AppHttpHeaderGroup extends StatelessWidget {
+  const AppHttpHeaderGroup({super.key, required this.name, required this.value, required this.remove});
+
+  final Widget name;
+  final Widget value;
+  final Widget remove;
+
+  @override
+  Widget build(BuildContext context) {
+    final palette = AppPalette.of(context);
+    return Container(
+      padding: const EdgeInsets.all(AppDesignTokens.space12),
+      decoration: BoxDecoration(
+        border: Border.all(color: palette.border),
+        borderRadius: BorderRadius.circular(AppDesignTokens.controlRadius),
+      ),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.stretch,
+        children: [
+          Row(
+            children: [
+              Expanded(child: Text(context.l10n.httpHeaderName)),
+              remove,
+            ],
+          ),
+          const SizedBox(height: AppDesignTokens.space4),
+          name,
+          const SizedBox(height: AppDesignTokens.space12),
+          Text(context.l10n.httpHeaderValue),
+          const SizedBox(height: AppDesignTokens.space8),
+          value,
+        ],
+      ),
+    );
+  }
+}