add day-detail view to monthly history calendar

날짜 셀 클릭 시 그 날 예정된 습관별 완료/실패/미완료 상태를 htmx로 불러와 보여준다.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/static/css/style.css

@@ -729,6 +729,42 @@ label {
   color: var(--color-text-muted);
 }
 
+.calendar-cell.clickable {
+  cursor: pointer;
+}
+
+.day-detail-card {
+  margin-top: var(--space-2);
+}
+
+.day-detail-list {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.day-detail-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 8px 0;
+  border-bottom: 1px solid var(--color-border);
+}
+
+.day-detail-item:last-child {
+  border-bottom: none;
+}
+
+.day-detail-status-checked {
+  color: var(--color-success);
+  border-color: var(--color-success);
+}
+
+.day-detail-status-missed {
+  color: var(--color-danger);
+  border-color: var(--color-danger);
+}
+
 /* 주별 매트릭스 */
 .week-matrix {
   width: 100%;