feat: add refresh button to ProblemSwitcher

XMOJ.user.js

@@ -2323,6 +2323,25 @@ async function main() {
                             }
                             problemSwitcher.innerHTML += `<a href="${problemList[i].url}" title="${problemList[i].title.trim()}" class="btn btn-outline-secondary mb-2 ${activeClass}">${buttonText}</a>`;
                         }
+                        let refreshBtn = document.createElement("a");
+                        refreshBtn.title = "刷新缓存";
+                        refreshBtn.classList.add("btn", "btn-outline-secondary", "mt-2");
+                        refreshBtn.innerHTML = "↻";
+                        refreshBtn.href = "#";
+                        refreshBtn.addEventListener("click", function(e) {
+                            e.preventDefault();
+                            let cid = SearchParams.get("cid");
+                            let keysToRemove = [];
+                            for (let k = 0; k < localStorage.length; k++) {
+                                let key = localStorage.key(k);
+                                if (key && key.startsWith("UserScript-Contest-" + cid + "-")) {
+                                    keysToRemove.push(key);
+                                }
+                            }
+                            keysToRemove.forEach(k => localStorage.removeItem(k));
+                            location.reload();
+                        });
+                        problemSwitcher.appendChild(refreshBtn);
                         document.body.appendChild(problemSwitcher);
                     }
                     if (document.querySelector("body > div > div.mt-3 > h2") != null) {