fix: window capture list not showing in video sources

Root cause: PowerShell command was wrapped in exec() with double-quote
escaping that silently failed. Rewrote using execFile() with args array
which requires no manual escaping.

Changes:
- electron/devices.js: use execFile('powershell.exe', [...args]) for
  window enumeration — eliminates quoting issues entirely
- Window list now returned INSIDE getDevices() video array (type='window')
  so they arrive together with cameras/screens in one IPC call
- StreamSettings: windows grouped from devices.video directly, with 🪟
  emoji prefix for visual distinction
- Added inline "↻ Обновить" button in video source field header to
  refresh devices+windows on demand without switching tabs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/styles/App.css

@@ -485,6 +485,32 @@ html, body, #root {
   border-radius: var(--radius-sm);
 }
 
+.field-label-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 4px;
+}
+.field-label-row .field-label { margin-bottom: 0; }
+
+.btn-inline-refresh {
+  padding: 2px 8px;
+  font-size: 11px;
+  background: transparent;
+  border: 1px solid var(--border);
+  color: var(--text-muted);
+  border-radius: var(--radius-sm);
+  cursor: pointer;
+  transition: all 0.15s;
+  white-space: nowrap;
+}
+.btn-inline-refresh:hover:not(:disabled) {
+  border-color: var(--accent);
+  color: var(--accent);
+  background: var(--accent-dim);
+}
+.btn-inline-refresh:disabled { opacity: 0.4; cursor: not-allowed; }
+
 .fields-row {
   display: flex;
   gap: 8px;