punch banner: revert broken '重试直连' button, keep status banner

The '重试直连' button couldn't resolve the FFI 'bind' symbol
in this file's scope (Dart top-level identifier resolution quirk
when bind is re-exported from models/model.dart through common.dart).

Even if it had compiled, the button wouldn't solve the user's
real problem: the punch fails because of network conditions
(CGNAT, double-NAT, symmetric NAT on either side), not because
of a 'force_relay' flag.

What stays working:
  - Green ⚡ banner when P2P succeeded
  - Orange ⚠ banner when relay fallback
  - File-transfer menu item is intercepted with a toast on relay

Next steps for the user to actually get P2P:
  - Test on the same LAN (not via 4G/5G or CGNAT)
  - Check router has UPnP enabled
  - If still fails, ask the hbbs maintainer to improve is_local
    detection (compare LAN subnets, not just public IP)

flutter/lib/desktop/widgets/punch_status_banner.dart

@@ -14,73 +14,40 @@
 //
 // The banner is reactive: it subscribes to the Rx<String> so it updates
 // automatically if the connection type changes (e.g. after a re-connect).
-//
-// In relay mode the banner exposes a "重试直连" button that calls
-// sessionReconnect(sessionId, forceRelay=false) — this resets the
-// is_force_relay flag and triggers a fresh punch attempt. Useful when the
-// previous attempt's punch failed and we want to try again without
-// restarting the app.
 
 import 'package:flutter/material.dart';
 import 'package:get/get.dart';
 
 import '../../common/shared_state.dart';
-import '../../models/model.dart';
 
 class PunchStatusBanner extends StatelessWidget {
   final String peerId;
-  final SessionID? sessionId;
-  const PunchStatusBanner(
-      {super.key, required this.peerId, this.sessionId});
+  const PunchStatusBanner({super.key, required this.peerId});
 
   @override
   Widget build(BuildContext context) {
     return Obx(() {
       final ct = ConnectionTypeState.find(peerId);
       if (!ct.isValid()) {
-        // Not connected yet — show nothing
         return const SizedBox.shrink();
       }
       final isDirect = ct.direct.value == ConnectionType.strDirect;
       if (isDirect) {
-        return _Banner(
-          color: const Color(0xFFE7F5EA), // light green
-          iconColor: const Color(0xFF1E8E3E),
-          icon: Icons.bolt,
-          text: 'P2P 直连成功 — 走的是两台机器之间的网络，可放心传文件',
-          sessionId: sessionId,
-        );
+        return const _P2PBanner();
       } else {
-        return _Banner(
-          color: const Color(0xFFFFF3E0), // light orange
-          iconColor: const Color(0xFFE65100),
-          icon: Icons.warning_amber_rounded,
-          text: '中继模式 — 视频/控制走服务器 21117 中转，请勿传大文件',
-          sessionId: sessionId,
-        );
+        return const _RelayBanner();
       }
     });
   }
 }
 
-class _Banner extends StatelessWidget {
-  final Color color;
-  final Color iconColor;
-  final IconData icon;
-  final String text;
-  final SessionID? sessionId;
-  const _Banner({
-    required this.color,
-    required this.iconColor,
-    required this.icon,
-    required this.text,
-    this.sessionId,
-  });
+class _P2PBanner extends StatelessWidget {
+  const _P2PBanner();
 
   @override
   Widget build(BuildContext context) {
     return Material(
-      color: color,
+      color: const Color(0xFFE7F5EA),
       elevation: 2,
       child: SafeArea(
         bottom: false,
@@ -89,43 +56,58 @@ class _Banner extends StatelessWidget {
           child: Row(
             mainAxisSize: MainAxisSize.min,
             children: [
-              Icon(icon, color: iconColor, size: 18),
+              const Icon(Icons.bolt, color: Color(0xFF1E8E3E), size: 18),
               const SizedBox(width: 8),
-              Flexible(
+              const Flexible(
                 child: Text(
-                  text,
+                  'P2P 直连成功 — 走的是两台机器之间的网络，可放心传文件',
                   style: TextStyle(
-                    color: iconColor,
+                    color: Color(0xFF1E8E3E),
                     fontSize: 13,
                     fontWeight: FontWeight.w500,
                   ),
                 ),
               ),
-              const SizedBox(width: 8),
-              TextButton.icon(
-                onPressed:
-                    sessionId == null ? null : () => _retryDirect(sessionId!),
-                icon: const Icon(Icons.refresh, size: 14),
-                label: const Text('重试直连', style: TextStyle(fontSize: 12)),
-                style: TextButton.styleFrom(
-                  foregroundColor: iconColor,
-                  padding:
-                      const EdgeInsets.symmetric(horizontal: 6, vertical: 0),
-                  minimumSize: const Size(0, 28),
-                  tapTargetSize: MaterialTapTargetSize.shrinkWrap,
-                ),
-              ),
             ],
           ),
         ),
       ),
     );
   }
-
-  void _retryDirect(SessionID sessionId) {
-    // Resets is_force_relay and triggers a fresh punch attempt.
-    bind.sessionReconnect(sessionId: sessionId, forceRelay: false);
-  }
 }
 
+class _RelayBanner extends StatelessWidget {
+  const _RelayBanner();
 
+  @override
+  Widget build(BuildContext context) {
+    return Material(
+      color: const Color(0xFFFFF3E0),
+      elevation: 2,
+      child: SafeArea(
+        bottom: false,
+        child: Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
+          child: Row(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              const Icon(Icons.warning_amber_rounded,
+                  color: Color(0xFFE65100), size: 18),
+              const SizedBox(width: 8),
+              const Flexible(
+                child: Text(
+                  '中继模式 — 视频/控制走服务器 21117 中转，请勿传大文件',
+                  style: TextStyle(
+                    color: Color(0xFFE65100),
+                    fontSize: 13,
+                    fontWeight: FontWeight.w500,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}