Fix workspace background feature for Android

- Add missing filesystem permissions in capabilities
  - fs:allow-applocaldata-read-recursive
  - fs:allow-applocaldata-write-recursive
  - fs:allow-write-file
  - fs:allow-mkdir
  - fs:allow-exists
  - fs:allow-remove

- Fix Android photo picker URI handling
  - Detect file type from binary signature (PNG, JPEG, WebP)
  - Use manual path construction to avoid path joining issues
  - Works with Android photo picker content:// URIs

- Improve error handling with detailed toast messages
  - Show specific error at each step (read, mkdir, write, db)
  - Better debugging on Android where console is unavailable

- Fix window activation behavior
  - Restore minimized windows when activated

- Remove unused imports in launcher component

src/stores/desktop/windowManager.ts

@@ -300,6 +300,7 @@ export const useWindowManagerStore = defineStore('windowManager', () => {
     const window = windows.value.find((w) => w.id === windowId)
     if (window) {
       window.zIndex = nextZIndex.value++
+      window.isMinimized = false
       activeWindowId.value = windowId
     }
   }