fix: remove duplicate submit handler that caused double task creation

The Save button already has type=submit which naturally triggers
form submission. The additional click handler dispatching submit
event caused handleTaskSubmit to run twice.

static/js/tasks.js

@@ -350,9 +350,6 @@ document.addEventListener("DOMContentLoaded", () => {
     document.getElementById("task-modal-close").addEventListener("click", closeTaskModal);
     document.getElementById("task-modal-cancel").addEventListener("click", closeTaskModal);
     document.getElementById("task-form").addEventListener("submit", handleTaskSubmit);
-    document.getElementById("task-save-btn").addEventListener("click", (e) => {
-        document.getElementById("task-form").dispatchEvent(new Event("submit", { cancelable: true }));
-    });
 
     document.getElementById("side-panel-close").addEventListener("click", closeSidePanel);
     document.getElementById("save-task-btn").addEventListener("click", saveTask);