refactor: move 'Rebroadcast events' setting to Startup & Behavior section

Move the rebroadcast setting from Flight Mode to Startup & Behavior as it's more about behavior than offline mode

src/components/Settings/OfflineModeSettings.tsx

@@ -105,19 +105,6 @@ const OfflineModeSettings: React.FC<OfflineModeSettingsProps> = ({ settings, onU
         </label>
       </div>
 
-      <div className="setting-group">
-        <label htmlFor="rebroadcastToAllRelays" className="checkbox-label">
-          <input
-            id="rebroadcastToAllRelays"
-            type="checkbox"
-            checked={settings.rebroadcastToAllRelays ?? false}
-            onChange={(e) => onUpdate({ rebroadcastToAllRelays: e.target.checked })}
-            className="setting-checkbox"
-          />
-          <span>Rebroadcast events while browsing</span>
-        </label>
-      </div>
-
       <div style={{ 
         marginTop: '1.5rem', 
         padding: '1rem',

src/components/Settings/StartupPreferencesSettings.tsx

@@ -36,6 +36,19 @@ const StartupPreferencesSettings: React.FC<StartupPreferencesSettingsProps> = ({
           <span>Start with highlights panel collapsed</span>
         </label>
       </div>
+
+      <div className="setting-group">
+        <label htmlFor="rebroadcastToAllRelays" className="checkbox-label">
+          <input
+            id="rebroadcastToAllRelays"
+            type="checkbox"
+            checked={settings.rebroadcastToAllRelays ?? false}
+            onChange={(e) => onUpdate({ rebroadcastToAllRelays: e.target.checked })}
+            className="setting-checkbox"
+          />
+          <span>Rebroadcast events while browsing</span>
+        </label>
+      </div>
     </div>
   )
 }