feat(system): add systemd service and installation script

- Add gitks systemd service unit file with security sandboxing
- Create environment configuration template for gitks service
- Add logrotate configuration for gitks application logs
- Implement installation script with service user creation
- Set up proper directory permissions and file ownership
- Configure automatic service startup and systemd integration

etc/logrotate.d/gitks

@@ -0,0 +1,22 @@
+# GitKS logrotate configuration
+# 
+# Rotates file-based application logs if gitks is configured
+# to write logs to a file instead of journald.
+#
+# Location: /etc/logrotate.d/gitks
+# Permissions: 0644 root:root
+
+/var/log/gitks/*.log {
+    daily
+    missingok
+    rotate 14
+    compress
+    delaycompress
+    notifempty
+    create 0640 gitks gitks
+    sharedscripts
+    postrotate
+        # Notify gitks to reopen log files if needed
+        /bin/systemctl kill -s HUP gitks.service 2>/dev/null || true
+    endscript
+}