fix: preload schema options when selector becomes visible (closes #244)

Schema dropdown showed an empty horizontal line because data was loaded
lazily on dropdown open, leaving the Reka UI Select with zero items in
popper mode. Eagerly preload via watchEffect when the schema selector
becomes visible so data is ready before the user opens the dropdown.

src/components/layout/EditorToolbar.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { computed } from "vue";
+import { computed, watchEffect } from "vue";
 import { useI18n } from "vue-i18n";
 import {
   Play,
@@ -75,6 +75,13 @@ const activeSchemaOptions = computed(() => {
   return getSchemaOptionsForDb(connection.id, schemaDatabaseKey.value);
 });
 
+watchEffect(() => {
+  const connection = props.activeConnection;
+  if (connection && showSchemaSelector.value && schemaDatabaseKey.value) {
+    loadSchemaOptions(connection.id, schemaDatabaseKey.value).catch(() => {});
+  }
+});
+
 const isActiveDatabaseDefault = computed(() => isDefaultDatabase(props.activeConnection, activeDatabaseValue.value));
 const toolbarStyle = computed(() => {
   const color = props.activeConnection?.color;