gitignore: stop tracking built artifacts (PSLauncher-X.Y.Z.exe, installer output)

Last commit accidentally captured two large binaries that landed in the
working tree during the self-update test prep:
- PSLauncher-0.6.0.exe at repo root
- installer/output/PSLauncher-Setup-0.5.0.exe

Neither belongs in version control. Add /PSLauncher-*.exe and
/installer/output/ to .gitignore and `git rm --cached` the existing
entries so the next push doesn't reupload them.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -39,3 +39,7 @@ server/builds/*
 # Binaires copiés par le post-publish à la racine du repo
 /PSLauncher.exe
 /PSLauncher.Updater.exe
+/PSLauncher-*.exe
+
+# Sortie de l'installeur Inno Setup
+/installer/output/