feat(app): add configurable global background wallpaper

apps/desktop/src/App.vue

@@ -140,6 +140,7 @@ import { Input } from "@/components/ui/input";
 import { SearchableSelect } from "@/components/ui/searchable-select";
 import type { HistoryEntry } from "@/lib/backend/tauri";
 import { resolveDefaultAiSchema, type AiAction } from "@/lib/ai/ai";
+import { useBackgroundImage } from "@/composables/useBackgroundImage";
 import ExternalSqlFileChangeDialog from "@/components/editor/ExternalSqlFileChangeDialog.vue";
 import { resolveWindowContext } from "@/lib/app/windowContext";
 import { openDetachedTabWindow } from "@/lib/app/detachedTabWindow";
@@ -172,6 +173,7 @@ const { t } = useI18n();
 const connectionStore = useConnectionStore();
 const queryStore = useQueryStore();
 const settingsStore = useSettingsStore();
+const { active: appBackgroundActive, backgroundObjectUrl: appBackgroundObjectUrl, backgroundImageStyle: appBackgroundImageStyle } = useBackgroundImage(settingsStore);
 const { uiFontFamilyPreview } = useUiFontFamilyPreview();
 const savedSqlStore = useSavedSqlStore();
 const promptTemplateStore = usePromptTemplateStore();
@@ -3386,6 +3388,9 @@ onUnmounted(() => {
 <template>
   <LoginPage v-if="setupRequired || (needsAuth && !authenticated)" :setup-mode="setupRequired" @authenticated="onLoginSuccess" />
   <div v-show="!setupRequired && (!needsAuth || authenticated)" class="fixed inset-0 h-screen w-screen overflow-hidden">
+    <div v-if="appBackgroundActive && appBackgroundObjectUrl" data-app-background class="pointer-events-none fixed inset-0 -z-10 overflow-hidden">
+      <div class="h-full w-full" :style="appBackgroundImageStyle"></div>
+    </div>
     <TooltipProvider :delay-duration="300">
       <div class="h-screen w-screen max-w-full min-w-[760px] min-h-[600px] flex flex-col bg-background text-foreground overflow-hidden" :class="{ 'dbx-desktop-window-frame': drawDesktopWindowFrame }" :style="appUiFontFamilyStyle">
         <AppToolbar