Read constraints from the published URDF rather than hard code them.

Also make the webui more responsive for small screens.

webui/frontend/src/index.css

@@ -0,0 +1,65 @@
+/* ── App shell ────────────────────────────────────────────────────────────── */
+.app-layout {
+  display: flex;
+  flex-direction: column;
+  height: 100vh;
+  padding: 8px;
+  gap: 8px;
+  overflow: hidden;
+}
+
+.app-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  flex-shrink: 0;
+}
+
+.app-video {
+  flex-shrink: 0;
+}
+
+.app-video video {
+  width: 100%;
+  max-height: 55vh;
+  background: #000;
+  display: block;
+}
+
+/* ── Controls row ─────────────────────────────────────────────────────────── */
+.controls-row {
+  display: flex;
+  justify-content: space-between;
+  align-items: flex-start;
+  gap: 16px;
+  flex: 1;
+  min-height: 0;
+}
+
+.control-panel {
+  min-width: 160px;
+}
+
+/* ── Mobile ───────────────────────────────────────────────────────────────── */
+@media (max-width: 640px) {
+  .app-layout {
+    height: auto;
+    min-height: 100dvh;
+    overflow-y: auto;
+  }
+
+  .app-video video {
+    max-height: 52vw; /* landscape-ish crop on portrait phone */
+  }
+
+  .controls-row {
+    flex-direction: column;
+    flex: none;
+    align-items: stretch;
+  }
+
+  .control-panel {
+    width: 100%;
+    min-width: unset;
+  }
+}