Add system tray, APK Installer, fix package visibility, new themes/fo…

…nts; bump to v1.3.0

- System tray (Linux): pure Go D-Bus StatusNotifierItem, no cgo/libappindicator.
  Close now offers Minimize to Tray vs Quit instead of always quitting.
- New APK Installer module: batch-install from a folder or hand-picked files,
  live per-file progress, select all/none.
- Fix Packages/App Inspector silently hiding packages disabled/uninstalled by
  Canta/Shizuku (pm list packages needs -u to see them). Added a state filter
  and per-row Restore/Enable/Disable/Uninstall actions.
- 6 new theme palettes (Nord, Tokyo Night, Solarized Dark/Light, Rosé Pine,
  Everforest - 26 total), custom text colour, 8 bundled display fonts,
  adjustable font size.
- Horizontal sidebar now shrinks label text progressively instead of
  scrolling when the window narrows; fixed a touchpad stuck-scrollbar-drag bug.
- Updated README and fixed stale Go 1.23 -> 1.25 build instructions.

Fix path injection in local file handler (CodeQL go/path-injection)

ServeFile's built-in ".." rejection only covers r.URL.Path, not a path handed
to it explicitly from a query param — validate p resolves to a real, regular
file before serving.

Update README.md

fix: downgrade vite to v5 - v8 breaks production build

fix: add separate desktop files for deb and AppImage

fix: use correct desktop files for deb and AppImage separately

fix: use correct Exec path in desktop file - was Exec=ATK should be E…

…xec=/opt/atk/ATK

fix: correct Exec path and Categories in desktop file

fix: use committed appicon in CI instead of generating placeholder

fix: replace broken appicon with proper 256x256 PNG