feat: generate RPM packages for CentOS 7, Rocky Linux 8/9/10

- Update Dockerfile.package to build RPMs for multiple distributions
  using a unified fpm-based approach
- Add RPM maintainer scripts (postinst, prerm, postrm) for proper
  installation and service management
- Update ja4sentinel.spec for CentOS 7+ compatibility
- Add packaging/systemd/config.yml as default configuration
- Update test-rpm.sh to test installation on all 4 target distributions
- Fix CentOS 7 repository configuration (EOL - vault.centos.org)

Generated RPMs:
- el7: CentOS 7 (libpcap >= 1.4.0)
- el8: Rocky Linux 8 (libpcap >= 1.9.0)
- el9: Rocky Linux 9 (libpcap >= 1.9.0)
- el10: AlmaLinux 10 / Rocky Linux 10 (libpcap >= 1.9.0)

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packaging/rpm/postrm

@@ -0,0 +1,18 @@
+#!/bin/bash
+#
+# postrm - Script de post-désinstallation RPM pour ja4sentinel
+# Compatible CentOS 7, Rocky Linux 8/9/10
+#
+
+set -e
+
+echo "==> ja4sentinel: Running post-removal script..."
+
+# Reload systemd after removal
+if [ -x /bin/systemctl ]; then
+    echo "==> ja4sentinel: Reloading systemd daemon..."
+    /bin/systemctl daemon-reload
+fi
+
+echo "==> ja4sentinel: Post-removal complete."
+exit 0