do not allow editing task item if task has logs.

svelte-ui/src/forms/TaskForm.svelte

@@ -108,7 +108,7 @@
     <label for="description">Description</label>
     <textarea disabled={deletion} name="description" bind:value={description} />
     <label for="itemId">Item</label>
-    <ItemSelect disabled={deletion} name="itemId" bind:value={itemId} />
+    <ItemSelect disabled={deletion || task.logs.length > 0} name="itemId" bind:value={itemId} />
     <label for="itemAmount">Amount</label>
     <input disabled={deletion} name="itemAmount" type="number" bind:value={itemAmount} />
     <label for="endTime">Deadline (Optional)</label>