Add invite email templates and delivery workflow

frontend/app/globals.css

@@ -4641,6 +4641,48 @@ button:hover:not(:disabled) {
   gap: 10px;
 }
 
+.invite-email-template-picker {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  margin-bottom: 12px;
+}
+
+.invite-email-template-picker button {
+  border-radius: 8px;
+}
+
+.invite-email-template-picker button.is-active {
+  border-color: rgba(135, 182, 255, 0.4);
+  background: rgba(86, 132, 220, 0.14);
+  color: #eef2f7;
+}
+
+.invite-email-template-meta {
+  display: grid;
+  gap: 4px;
+  margin-bottom: 10px;
+}
+
+.invite-email-template-meta h3 {
+  margin: 0;
+}
+
+.invite-email-placeholder-list {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+}
+
+.invite-email-placeholder-list code {
+  padding: 6px 8px;
+  border: 1px solid rgba(255, 255, 255, 0.08);
+  border-radius: 8px;
+  background: rgba(255, 255, 255, 0.04);
+  color: #d6dde8;
+  font-size: 0.78rem;
+}
+
 .admin-panel > h2 + .lede {
   margin-top: -2px;
 }