refactor: collapse micro-modules, add AUR packaging

- domain/ (7 files) → domain.rs + error.rs + window.rs
- protocols/sftp/ (4 files) → sftp.rs, ftp/ (3 files) → ftp.rs
- storage/db/ (6 files) → storage.rs + settings.rs
- transfer/ (5 files) → transfers/{queue,worker}.rs
- add dist/PKGBUILD, .SRCINFO, wherry.desktop for AUR
- fix all import paths, 53 tests pass

.gitignore

@@ -1,5 +1,9 @@
 node_modules/
-dist/
+dist/*.tar.gz
+dist/*.zip
+dist/*.deb
+dist/*.rpm
+dist/pkg/
 target/
 .tauri/
 src/target/