feat: .deb paketi + kurulum talimatı

deb/DEBIAN/postinst

@@ -0,0 +1,15 @@
+#!/bin/sh
+set -e
+
+# Varsayılan görüntü izleyici olarak ayarla
+for mime in image/png image/jpeg image/jpg image/webp image/bmp image/gif; do
+  xdg-mime default imajviewer.desktop "$mime" 2>/dev/null || true
+done
+
+# Masaüstü veritabanını güncelle
+which update-desktop-database >/dev/null 2>&1 && \
+  update-desktop-database /usr/share/applications/ 2>/dev/null || true
+which gtk-update-icon-cache >/dev/null 2>&1 && \
+  gtk-update-icon-cache /usr/share/icons/hicolor/ 2>/dev/null || true
+
+exit 0