Camera live view (test): MJPEG over TCP from tool/camview_server.py, exposure and gain controls

Its own paced connection beside the boundary (project-yukart decision 27,
proposed); latest-wins per client, SO_MAX_PACING_RATE 4 MB/s.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

lib/main.dart

@@ -6,6 +6,7 @@ import 'dart:math';
 import 'package:flutter/material.dart';
 
 import 'boundary.dart';
+import 'camview.dart';
 import 'linktest.dart';
 import 'net.dart';
 
@@ -170,6 +171,13 @@ class LinkBar extends StatelessWidget {
               icon: const Icon(Icons.speed),
               label: const Text('Link test'),
             ),
+            TextButton.icon(
+              onPressed: () => Navigator.of(context).push(
+                MaterialPageRoute<void>(builder: (_) => CamViewPage(host: Uri.parse(b.url).host)),
+              ),
+              icon: const Icon(Icons.videocam),
+              label: const Text('Camera'),
+            ),
           ]),
         ),
       ),