feat: implement local terminal support with shell configuration and UI integration

frontend/src/css/forms.css

@@ -467,6 +467,16 @@
   color: var(--danger);
 }
 
+.settings-shell-row {
+  display: flex;
+  gap: var(--space-2);
+  align-items: center;
+}
+
+.settings-shell-row .form-input {
+  flex: 1;
+}
+
 .form-success {
   font-size: var(--text-xs);
   color: var(--success);

frontend/src/css/sidebar.css

@@ -253,6 +253,12 @@
 .sidebar-item .protocol-indicator.proto-github::before {
   content: "GH";
 }
+.sidebar-item .protocol-indicator.proto-vnc::before {
+  content: "⊞";
+}
+.sidebar-item .protocol-indicator.proto-local::before {
+  content: "›_";
+}
 
 .sidebar-item .protocol-indicator.proto-ssh {
   background: rgba(78, 205, 196, 0.18);
@@ -270,6 +276,21 @@
   background: rgba(124, 138, 255, 0.18);
   color: var(--protocol-github);
 }
+.sidebar-item .protocol-indicator.proto-vnc {
+  background: rgba(232, 93, 74, 0.18);
+  color: var(--protocol-vnc);
+}
+.sidebar-item .protocol-indicator.proto-local {
+  background: rgba(139, 195, 74, 0.18);
+  color: var(--protocol-local);
+}
+
+/* Local machine item separator */
+.sidebar-item-local {
+  border-bottom: 1px solid var(--border-subtle);
+  margin: var(--space-2) var(--space-2) var(--space-2);
+  padding-bottom: var(--space-2);
+}
 
 /* Text block (name + host) */
 .sidebar-item-text {

frontend/src/css/tabs.css

@@ -114,6 +114,14 @@
   background: rgba(124, 138, 255, 0.15);
   color: var(--protocol-github);
 }
+.tab-badge.badge-vnc {
+  background: rgba(232, 93, 74, 0.15);
+  color: var(--protocol-vnc);
+}
+.tab-badge.badge-local {
+  background: rgba(139, 195, 74, 0.15);
+  color: var(--protocol-local);
+}
 
 /* -----------------------------------------------------------------------
    Status dot (connection state)

frontend/src/css/tokens.css

@@ -58,6 +58,7 @@
   --protocol-raw: #ab47bc;
   --protocol-github: #7c8aff;
   --protocol-vnc: #e85d4a;
+  --protocol-local: #8bc34a;
 
   /* -----------------------------------------------------------------------
        Spacing scale (4 px base unit)