fix: recover gateway callbacks and client send flows

src/styles/components.css

@@ -742,6 +742,24 @@
   width: min(360px, calc(100vw - 48px));
 }
 
+@media (max-width: 780px) {
+  .ui-date-time-popover {
+    inset: auto 12px;
+    max-height: calc(100dvh - 24px);
+    overflow-y: auto;
+    position: fixed;
+    top: 12px;
+    width: auto;
+  }
+
+  .ui-date-time-popover .ui-date-range-actions {
+    background: var(--color-surface);
+    bottom: 0;
+    padding-top: var(--space-2);
+    position: sticky;
+  }
+}
+
 .ui-time-picker {
   align-items: center;
   border: 1px solid var(--color-border);

src/styles/global.css

@@ -574,10 +574,17 @@
 }
 
 .send-submit-row {
+  align-items: center;
   display: flex;
+  gap: var(--space-3);
   justify-content: flex-end;
 }
 
+.send-submit-hint {
+  color: var(--color-text-muted);
+  font-size: var(--font-size-sm);
+}
+
 .mms-send-page .send-card {
   box-shadow: none;
 }