feat: add bulk date management functionality and update admin interface

public/admin.css

@@ -225,11 +225,101 @@
   background: #fff0f2;
 }
 
+.delete-date-btn.is-booked,
+.delete-date-btn.is-booked:hover,
+.delete-date-btn.is-booked:focus-visible {
+  border-color: #bdb7b2;
+  background: #e3e0dd;
+  color: #88827d;
+  cursor: not-allowed;
+}
+
 .empty-dates {
   margin: 18px 0 0;
   color: var(--color-text-light);
 }
 
+.admin-calendar {
+  margin-top: 20px;
+  padding: 16px;
+  background: #fffefa;
+  border: 1px solid #eaded1;
+  border-radius: 8px;
+}
+
+.calendar-header,
+.weekday-row,
+.day-grid {
+  display: grid;
+  grid-template-columns: repeat(7, 1fr);
+  gap: 4px;
+}
+
+.calendar-header {
+  grid-template-columns: 40px 1fr 40px;
+  align-items: center;
+  margin-bottom: 12px;
+}
+
+.month-label {
+  margin: 0;
+  color: var(--color-rose-dark);
+  font-size: 1.05rem;
+  text-align: center;
+}
+
+.month-nav-btn {
+  width: 40px;
+  height: 40px;
+  border: 0;
+  border-radius: 50%;
+  background: var(--color-rose-light);
+  color: var(--color-rose-dark);
+  font-size: 1.2rem;
+  cursor: pointer;
+}
+
+.month-nav-btn:disabled { opacity: 0.35; cursor: not-allowed; }
+.weekday-row { margin-bottom: 6px; }
+.weekday-row span { text-align: center; color: var(--color-text-light); font-size: 0.78rem; font-weight: 700; }
+
+.day-cell {
+  position: relative;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  aspect-ratio: 1;
+  border: 0;
+  border-radius: 50%;
+  background: transparent;
+  color: var(--color-text);
+  font: inherit;
+  font-weight: 700;
+  cursor: pointer;
+}
+
+.day-cell.is-empty { pointer-events: none; }
+.day-cell.is-disabled { color: #d9c3cb; cursor: not-allowed; }
+.day-cell.is-today { box-shadow: inset 0 0 0 2px var(--color-rose); }
+.day-cell.is-short { background: linear-gradient(90deg, var(--color-rose) 0 50%, var(--color-rose-light) 50%); color: var(--color-white); }
+.day-cell.is-long { background: linear-gradient(135deg, var(--color-rose) 0%, var(--color-rose-dark) 100%); color: var(--color-white); }
+.day-cell.is-booked { background: #4b9b68; color: var(--color-white); cursor: not-allowed; }
+
+.calendar-legend {
+  display: flex;
+  gap: 18px;
+  margin: 12px 0 16px;
+  color: var(--color-text-light);
+  font-size: 0.85rem;
+}
+
+.calendar-legend span { display: inline-flex; align-items: center; gap: 6px; }
+.legend-dot { width: 16px; height: 16px; border-radius: 50%; }
+.legend-dot.is-short { background: linear-gradient(90deg, var(--color-rose) 0 50%, var(--color-rose-light) 50%); }
+.legend-dot.is-long { background: var(--color-rose-dark); }
+
+.date-type-label { color: var(--color-text-light); font-weight: 700; }
+
 .hidden {
   display: none !important;
 }