Add step_snap: list saved + forget per id

Co-Authored-By: Claude <noreply@anthropic.com>

cleanup-server

@@ -267,6 +267,33 @@ step_pkg_cache() {
     echo ""
 }
 
+# -----------------------------
+# Bước 5: Snap — forget từng snapshot
+# -----------------------------
+step_snap() {
+    echo "${C_TITLE}--- [Snap] ---${C_RESET}"
+    if ! command -v snap >/dev/null 2>&1; then
+        echo "${C_WARN}    ⚠ snap not found.${C_RESET}"
+        echo ""
+        return
+    fi
+    local saved
+    saved=$(sudo snap saved 2>/dev/null | awk 'NR>1{print $1}')
+    if [ -z "$saved" ]; then
+        echo "${C_OK}    ✓ Không có snap snapshot nào.${C_RESET}"
+        echo ""
+        return
+    fi
+    local id
+    for id in $saved; do
+        if confirm_yn "Forget snap snapshot (Set $id)?"; then
+            sudo snap forget "$id"
+        fi
+    done
+    echo "${C_OK}    ✓ Snap cleanup xong.${C_RESET}"
+    echo ""
+}
+
 # -----------------------------
 # Chạy tuần tự 6 bước (stub — các bước thêm ở Task 4-9)
 # -----------------------------
@@ -275,6 +302,7 @@ run_all_steps() {
     step_docker
     step_journal
     step_pkg_cache
+    step_snap
 }
 
 # -----------------------------