feat: replace status dropdown with one-click toggle buttons

Replace <select> in side panel with 4 toggle buttons (To Do / Doing /
Pending / Done). Clicking a button immediately sends the PATCH status
API call. Active button is highlighted with status-specific colors and
shadow. saveTask now only handles title/description changes.

static/js/tasks.js

@@ -234,9 +234,12 @@ function selectTask(taskId) {
 
     document.getElementById("edit-task-title").value = task.title;
     document.getElementById("edit-task-desc").value = task.desc || "";
-    document.getElementById("edit-task-status").value = task.status;
     document.getElementById("side-panel-error").textContent = "";
 
+    document.querySelectorAll(".status-btn").forEach(btn => {
+        btn.classList.toggle("active", btn.dataset.status === task.status);
+    });
+
     const sidePanel = document.getElementById("side-panel");
     if (!sidePanel.classList.contains("active")) {
         sidePanel.classList.add("active");
@@ -257,7 +260,6 @@ async function saveTask() {
 
     const title = document.getElementById("edit-task-title").value.trim();
     const desc = document.getElementById("edit-task-desc").value;
-    const status = document.getElementById("edit-task-status").value;
 
     if (!title) {
         error.textContent = "Title is required";
@@ -266,12 +268,24 @@ async function saveTask() {
 
     try {
         await put(`/api/tasks/${selectedTaskId}`, { title, desc });
+        await loadTasks();
+    } catch (err) {
+        error.textContent = err.message;
+    }
+}
 
-        const currentTask = tasks.find(t => t.id === selectedTaskId);
-        if (status !== currentTask?.status) {
-            await patch(`/api/tasks/${selectedTaskId}/status`, { status });
-        }
+async function setTaskStatus(status) {
+    if (!selectedTaskId) return;
 
+    const error = document.getElementById("side-panel-error");
+    error.textContent = "";
+
+    document.querySelectorAll(".status-btn").forEach(btn => {
+        btn.classList.toggle("active", btn.dataset.status === status);
+    });
+
+    try {
+        await patch(`/api/tasks/${selectedTaskId}/status`, { status });
         await loadTasks();
     } catch (err) {
         error.textContent = err.message;