feat(app): add configurable global background wallpaper

apps/desktop/src/lib/backend/api.ts

@@ -326,6 +326,10 @@ export const loadPinnedTreeNodeIds = forward("loadPinnedTreeNodeIds");
 export const savePinnedTreeNodeIds = forward("savePinnedTreeNodeIds");
 export const loadEditorSettings = forward("loadEditorSettings");
 export const saveEditorSettings = forward("saveEditorSettings");
+export const saveBackgroundImage = forward("saveBackgroundImage");
+export const clearBackgroundImage = forward("clearBackgroundImage");
+export const readBackgroundImage = forward("readBackgroundImage");
+export const checkBackgroundImage = forward("checkBackgroundImage");
 export const loadOpenTabsState = forward("loadOpenTabsState");
 export const saveOpenTabsState = forward("saveOpenTabsState");
 export const saveDetachedTabHandoff = forward("saveDetachedTabHandoff");

apps/desktop/src/lib/backend/http.ts

@@ -1881,6 +1881,28 @@ export async function saveEditorSettings(settings: unknown): Promise<void> {
   await saveBrowserAppState("editor_settings", settings);
 }
 
+// Background images are desktop-only: the web backend has no local data dir.
+export interface BackgroundImageInfo {
+  storedPath: string;
+  fileName: string;
+}
+
+export async function saveBackgroundImage(_sourcePath: string): Promise<BackgroundImageInfo> {
+  throw new Error("Background images are only supported in the desktop app");
+}
+
+export async function clearBackgroundImage(_storedPath: string): Promise<void> {
+  throw new Error("Background images are only supported in the desktop app");
+}
+
+export async function readBackgroundImage(_storedPath: string): Promise<string> {
+  throw new Error("Background images are only supported in the desktop app");
+}
+
+export async function checkBackgroundImage(_storedPath: string): Promise<boolean> {
+  throw new Error("Background images are only supported in the desktop app");
+}
+
 export async function loadOpenTabsState(): Promise<OpenTabsStatePayload | null> {
   const value = await loadBrowserAppState("open_tabs");
   if (!value || typeof value !== "object") return null;

apps/desktop/src/lib/backend/tauri.ts

@@ -740,6 +740,27 @@ export async function saveEditorSettings(settings: unknown): Promise<void> {
   return invoke("save_editor_settings", { settings });
 }
 
+export interface BackgroundImageInfo {
+  storedPath: string;
+  fileName: string;
+}
+
+export async function saveBackgroundImage(sourcePath: string): Promise<BackgroundImageInfo> {
+  return invoke("save_background_image", { sourcePath });
+}
+
+export async function clearBackgroundImage(storedPath: string): Promise<void> {
+  return invoke("clear_background_image", { storedPath });
+}
+
+export async function readBackgroundImage(storedPath: string): Promise<string> {
+  return invoke("read_background_image", { storedPath });
+}
+
+export async function checkBackgroundImage(storedPath: string): Promise<boolean> {
+  return invoke("check_background_image", { storedPath });
+}
+
 export async function loadOpenTabsState(): Promise<OpenTabsStatePayload | null> {
   return invoke("load_open_tabs_state");
 }