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-tauri/capabilities/default.json

@@ -18,8 +18,14 @@
     "fs:allow-appconfig-write-recursive",
     "fs:allow-appdata-read-recursive",
     "fs:allow-appdata-write-recursive",
+    "fs:allow-applocaldata-read-recursive",
+    "fs:allow-applocaldata-write-recursive",
     "fs:allow-read-file",
+    "fs:allow-write-file",
     "fs:allow-read-dir",
+    "fs:allow-mkdir",
+    "fs:allow-exists",
+    "fs:allow-remove",
     "fs:allow-resource-read-recursive",
     "fs:allow-resource-write-recursive",
     "fs:allow-download-read-recursive",