feat(calendar): header continuity with week numbers + skeleton content in fly-rect

- Add ISO week numbers to the left of week rows in month view (8, 9, 10...)
  with spacer alignment on day-of-week headers
- Inject label + skeleton placeholder lines into fly-rect during zoom animations:
  zoom-in shows source label (month name / "Week N" / day name) + pulsing bars
  zoom-out shows target context label + skeleton
- Skeleton CSS uses pulse animation (0.8s alternate) for loading hint
- Non-scoped style block for dynamically injected innerHTML elements
- isoWeekNumber helper for ISO 8601 week calculation
- Extended MonthRow type with weekNumber property

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/app/components/workspace/calendar/CrmCalendarPanel.vue

@@ -25,6 +25,7 @@ type MonthCell = {
 type MonthRow = {
   key: string;
   startKey: string;
+  weekNumber: number;
   cells: MonthCell[];
 };
 
@@ -220,21 +221,24 @@ defineProps<{
                   data-calendar-layer="month"
                   :class="calendarView === 'month' || calendarView === 'agenda' ? 'calendar-depth-layer-active' : 'calendar-depth-layer-hidden'"
                 >
-                  <div class="grid grid-cols-7 gap-1 text-center text-xs font-semibold text-base-content/60">
-                    <span>Sun</span>
-                    <span>Mon</span>
-                    <span>Tue</span>
-                    <span>Wed</span>
-                    <span>Thu</span>
-                    <span>Fri</span>
-                    <span>Sat</span>
+                  <div class="flex items-center gap-1">
+                    <span class="calendar-week-number" aria-hidden="true"></span>
+                    <div class="grid grid-cols-7 gap-1 text-center text-xs font-semibold text-base-content/60 flex-1">
+                      <span>Sun</span>
+                      <span>Mon</span>
+                      <span>Tue</span>
+                      <span>Wed</span>
+                      <span>Thu</span>
+                      <span>Fri</span>
+                      <span>Sat</span>
+                    </div>
                   </div>
 
                   <div class="flex flex-1 flex-col gap-1">
                     <div
                       v-for="row in monthRows"
                       :key="row.key"
-                      class="group relative flex-1 calendar-hover-targetable"
+                      class="group relative flex-1 flex items-stretch gap-1 calendar-hover-targetable"
                       :class="[
                         calendarHoveredWeekStartKey === row.startKey ? 'calendar-hover-target' : '',
                         calendarZoomPrimeToken === calendarPrimeWeekToken(row.startKey) ? 'calendar-zoom-prime-active' : '',
@@ -243,7 +247,8 @@ defineProps<{
                       :data-calendar-week-start-key="row.startKey"
                       @mouseenter="setCalendarHoveredWeekStartKey(row.startKey)"
                     >
-                      <div class="grid grid-cols-7 gap-1 h-full">
+                      <span class="calendar-week-number">{{ row.weekNumber }}</span>
+                      <div class="grid grid-cols-7 gap-1 h-full flex-1">
                         <button
                           v-for="cell in row.cells"
                           :key="cell.key"
@@ -440,6 +445,18 @@ defineProps<{
   right: 4px;
 }
 
+.calendar-week-number {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 24px;
+  min-width: 24px;
+  font-size: 10px;
+  font-weight: 500;
+  color: color-mix(in oklab, var(--color-base-content) 40%, transparent);
+  user-select: none;
+}
+
 .calendar-hover-targetable {
   transform-origin: center center;
   transition: transform 320ms ease, box-shadow 320ms ease, outline-color 320ms ease;
@@ -563,3 +580,44 @@ defineProps<{
   }
 }
 </style>
+
+<style>
+/* Non-scoped: fly-rect inner content is injected via innerHTML */
+.calendar-fly-rect .calendar-fly-content {
+  display: flex;
+  flex-direction: column;
+  padding: 12px 16px;
+  height: 100%;
+  box-sizing: border-box;
+  overflow: hidden;
+}
+
+.calendar-fly-rect .calendar-fly-label {
+  font-size: 14px;
+  font-weight: 600;
+  color: var(--color-base-content);
+  margin: 0 0 12px 0;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.calendar-fly-rect .calendar-fly-skeleton {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  flex: 1;
+}
+
+.calendar-fly-rect .calendar-fly-skeleton-line {
+  height: 8px;
+  border-radius: 4px;
+  background: color-mix(in oklab, var(--color-base-content) 10%, transparent);
+  animation: calendar-fly-skeleton-pulse 0.8s ease-in-out infinite alternate;
+}
+
+@keyframes calendar-fly-skeleton-pulse {
+  from { opacity: 0.3; }
+  to { opacity: 0.7; }
+}
+</style>