Fix VirtViewer detection on Windows + manual path override

VirtViewer's installer folder name includes the version number
(e.g. "VirtViewer v11.0-256"), so the previous hardcoded path never
matched a real install. Now scans Program Files for any VirtViewer*
folder, and adds a Settings dialog (Windows only) to pick the
remote-viewer.exe path manually as a fallback.

src/renderer/styles.css

@@ -292,3 +292,59 @@ body.vms-page {
   margin-top: 0.5rem;
   color: #3a4a60;
 }
+
+/* ── Settings modal ───────────────────────────────────────── */
+.modal-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(5, 8, 16, 0.65);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 10;
+}
+
+.modal-card {
+  width: 420px;
+  max-width: 90vw;
+  background: var(--bg-card);
+  border: 1px solid var(--border);
+  border-radius: 14px;
+  padding: 1.6rem 1.7rem;
+  box-shadow: 0 24px 60px rgba(0,0,0,0.55);
+}
+
+.modal-card h3 {
+  font-size: 1rem;
+  font-weight: 600;
+  margin-bottom: 0.6rem;
+}
+
+.modal-card .hint {
+  font-size: 0.8rem;
+  color: var(--muted);
+  margin-bottom: 1.1rem;
+  line-height: 1.5;
+}
+
+.path-display {
+  padding: 0.6rem 0.85rem;
+  background: var(--bg-input);
+  border: 1px solid var(--border);
+  border-radius: 7px;
+  font-size: 0.82rem;
+  color: var(--text);
+  word-break: break-all;
+}
+
+.modal-actions {
+  display: flex;
+  gap: 0.5rem;
+  justify-content: flex-end;
+  margin-top: 1.4rem;
+}
+
+.modal-actions .modal-close {
+  width: auto;
+  padding: 0.42rem 1rem;
+}