优化 Debian 包管理，简化发行版配置

- CI：简化 Debian 包发布流程，统一使用 stable 发行版
- 移除 bookworm 和 trixie 多发行版支持，简化维护
- postinst：优化安装完成提示，提供清晰的配置和启动步骤
- postrm/prerm：改进卸载和升级前的清理逻辑
- README：更新安装说明，使用 stable 仓库
- install.deb.sh：同步更新仓库配置

debian/postrm

@@ -3,28 +3,33 @@ set -e
 
 case "$1" in
     purge)
-        # Remove log directory
-        rm -rf /var/log/xxxigcc
-
-        # Remove config directory
-        rm -rf /etc/xxxigcc
-
         # Remove user and group
         if getent passwd xxxigcc >/dev/null; then
-            deluser --system xxxigcc 2>/dev/null || true
+            deluser --quiet xxxigcc || true
         fi
 
         if getent group xxxigcc >/dev/null; then
-            delgroup --system xxxigcc 2>/dev/null || true
+            delgroup --quiet xxxigcc || true
         fi
+
+        # Remove data directories (only on purge)
+        rm -rf /var/log/xxxigcc
+        rm -rf /etc/xxxigcc
         ;;
 
     remove|upgrade|failed-upgrade|abort-install|abort-upgrade|disappear)
-        # Reload systemd
-        if [ -d /run/systemd/system ]; then
-            systemctl daemon-reload
-        fi
+        # Do nothing
+        ;;
+
+    *)
+        echo "postrm called with unknown argument \`$1'" >&2
+        exit 1
         ;;
 esac
 
-exit 0
+# Reload systemd
+if [ -d /run/systemd/system ]; then
+    systemctl daemon-reload
+fi
+
+exit 0