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.

README.md

@@ -86,7 +86,7 @@ The binary is written to:
 
 ```text
 # GUI executable produced by scripts\build-windows.bat.
-dist\windows\pysentry-0.2.1-windows-amd64.exe
+dist\windows\pysentry-0.2.2-windows-amd64.exe
 ```
 
 Linux:
@@ -101,7 +101,7 @@ The binary is written to:
 
 ```text
 # Linux executable produced by scripts/build-linux.sh.
-dist/linux/pysentry-0.2.1-linux-amd64
+dist/linux/pysentry-0.2.2-linux-amd64
 ```
 
 Linux using Docker:
@@ -118,7 +118,7 @@ The binary is copied to:
 
 ```text
 # Linux executable copied out of the Docker build image.
-dist\linux\pysentry-0.2.1-linux-amd64
+dist\linux\pysentry-0.2.2-linux-amd64
 ```
 
 Release build from Linux:
@@ -143,13 +143,13 @@ The binaries are copied to:
 
 ```text
 # Linux artifact.
-dist/linux/pysentry-0.2.1-linux-amd64
+dist/linux/pysentry-0.2.2-linux-amd64
 
 # Linux arm64 artifact.
-dist/linux/pysentry-0.2.1-linux-arm64
+dist/linux/pysentry-0.2.2-linux-arm64
 
 # Windows artifact cross-compiled from Linux.
-dist/windows/pysentry-0.2.1-windows-amd64.exe
+dist/windows/pysentry-0.2.2-windows-amd64.exe
 ```
 
 ## Run From Source
@@ -292,7 +292,7 @@ Linux:
 [Desktop Entry]
 Type=Application
 Name=PySentry
-Exec=/opt/pysentry/pysentry-0.2.1-linux-amd64
+Exec=/opt/pysentry/pysentry-0.2.2-linux-amd64
 Terminal=false
 ```