add abandoned status to distinguish given-up habits from completed ones

Completed and abandoned habits were both lumped under a single terminal
state, making it impossible to tell "finished successfully" apart from
"gave up" when reviewing habit history.

app/templates/partials/habit_item.html

@@ -41,6 +41,14 @@
         hx-swap="none"
         hx-confirm="'{{ habit.name }}' 습관을 완료 처리할까요?"
       >완료 처리</button>
+      <button
+        type="button"
+        class="btn btn-secondary"
+        hx-post="/habits/{{ habit.id }}/abandon"
+        hx-target="body"
+        hx-swap="none"
+        hx-confirm="'{{ habit.name }}' 습관을 포기할까요?"
+      >포기</button>
       {% else %}
       <button
         type="button"