Release version 0.2.2

Add Linux desktop integration that installs a user-level .desktop file and icon under XDG data directories so taskbars can match the PySentry window to the application icon.

Pass the installed icon path into Linux autostart desktop entries when available, while keeping the Windows and fallback autostart APIs compatible.

Bump the application version to 0.2.2, update README artifact examples, and record the release notes in docs/CHANGELOG.md. Also adjust the Mermaid architecture diagram so Gitea can render it without invalid SVG line-break tags.

assets/assets.go

@@ -24,3 +24,7 @@ func Icon() fyne.Resource {
 	// resources rather than Fyne runtime state.
 	return fyne.NewStaticResource("pysentry-icon.png", iconBytes)
 }
+
+func IconBytes() []byte {
+	return append([]byte(nil), iconBytes...)
+}