frontend: add pan+wheel zoom canvas interaction for calendar

frontend/app.vue

@@ -2129,6 +2129,88 @@ const calendarZoomLabel = computed(() => {
   return "Year";
 });
 
+const calendarPanMode = ref(false);
+const calendarCanvasRef = ref<HTMLElement | null>(null);
+const calendarCanvasScale = ref(1);
+const calendarCanvasOffsetX = ref(0);
+const calendarCanvasOffsetY = ref(0);
+const calendarCanvasDragging = ref(false);
+let calendarCanvasPointerId: number | null = null;
+let calendarCanvasDragStartX = 0;
+let calendarCanvasDragStartY = 0;
+let calendarCanvasStartOffsetX = 0;
+let calendarCanvasStartOffsetY = 0;
+
+const calendarCanvasStyle = computed(() => ({
+  transform: `translate(${calendarCanvasOffsetX.value}px, ${calendarCanvasOffsetY.value}px) scale(${calendarCanvasScale.value})`,
+}));
+
+function clampCalendarCanvasScale(next: number) {
+  return Math.max(0.72, Math.min(2.35, Number(next) || 1));
+}
+
+function resetCalendarCanvas() {
+  calendarCanvasScale.value = 1;
+  calendarCanvasOffsetX.value = 0;
+  calendarCanvasOffsetY.value = 0;
+  calendarCanvasDragging.value = false;
+  calendarCanvasPointerId = null;
+}
+
+function toggleCalendarPanMode() {
+  calendarPanMode.value = !calendarPanMode.value;
+  if (!calendarPanMode.value) {
+    calendarCanvasDragging.value = false;
+    calendarCanvasPointerId = null;
+  }
+}
+
+function onCalendarCanvasWheel(event: WheelEvent) {
+  const host = calendarCanvasRef.value;
+  if (!host) return;
+
+  const rect = host.getBoundingClientRect();
+  const pivotX = event.clientX - rect.left;
+  const pivotY = event.clientY - rect.top;
+  const prevScale = calendarCanvasScale.value;
+  const ratio = event.deltaY < 0 ? 1.08 : 0.92;
+  const nextScale = clampCalendarCanvasScale(prevScale * ratio);
+  if (Math.abs(nextScale - prevScale) < 0.0001) return;
+
+  const contentX = (pivotX - calendarCanvasOffsetX.value) / prevScale;
+  const contentY = (pivotY - calendarCanvasOffsetY.value) / prevScale;
+  calendarCanvasScale.value = nextScale;
+  calendarCanvasOffsetX.value = pivotX - contentX * nextScale;
+  calendarCanvasOffsetY.value = pivotY - contentY * nextScale;
+}
+
+function onCalendarCanvasPointerDown(event: PointerEvent) {
+  if (!calendarPanMode.value || event.button !== 0) return;
+  const target = event.currentTarget as HTMLElement | null;
+  if (!target) return;
+
+  calendarCanvasDragging.value = true;
+  calendarCanvasPointerId = event.pointerId;
+  calendarCanvasDragStartX = event.clientX;
+  calendarCanvasDragStartY = event.clientY;
+  calendarCanvasStartOffsetX = calendarCanvasOffsetX.value;
+  calendarCanvasStartOffsetY = calendarCanvasOffsetY.value;
+  target.setPointerCapture(event.pointerId);
+}
+
+function onCalendarCanvasPointerMove(event: PointerEvent) {
+  if (!calendarPanMode.value || !calendarCanvasDragging.value || calendarCanvasPointerId !== event.pointerId) return;
+  calendarCanvasOffsetX.value = calendarCanvasStartOffsetX + (event.clientX - calendarCanvasDragStartX);
+  calendarCanvasOffsetY.value = calendarCanvasStartOffsetY + (event.clientY - calendarCanvasDragStartY);
+}
+
+function stopCalendarCanvasDrag(event?: PointerEvent) {
+  if (!calendarCanvasDragging.value) return;
+  if (event && calendarCanvasPointerId !== event.pointerId) return;
+  calendarCanvasDragging.value = false;
+  calendarCanvasPointerId = null;
+}
+
 const monthCells = computed(() => {
   const year = calendarCursor.value.getFullYear();
   const month = calendarCursor.value.getMonth();
@@ -4003,6 +4085,15 @@ async function decideFeedCard(card: FeedCard, decision: "accepted" | "rejected")
               </div>
 
               <div class="justify-self-end flex items-center gap-2">
+                <button
+                  class="btn btn-xs"
+                  :class="calendarPanMode ? 'btn-primary' : 'btn-ghost'"
+                  :title="calendarPanMode ? 'Disable pan mode' : 'Enable pan mode'"
+                  @click.stop="toggleCalendarPanMode"
+                >
+                  Pan
+                </button>
+                <button class="btn btn-xs btn-ghost" title="Reset canvas" @click.stop="resetCalendarCanvas">Reset</button>
                 <span class="text-[10px] uppercase tracking-wide text-base-content/60">Zoom</span>
                 <div class="flex items-center gap-2 rounded-lg border border-base-300 bg-base-100 px-2 py-1">
                   <input
@@ -4050,7 +4141,21 @@ async function decideFeedCard(card: FeedCard, decision: "accepted" | "rejected")
               >
                 <span>→</span>
               </button>
-	            <div class="calendar-content-scroll min-h-0 h-full overflow-y-auto pr-1">
+	            <div
+                class="calendar-content-scroll min-h-0 h-full overflow-y-auto pr-1"
+                :class="calendarPanMode ? (calendarCanvasDragging ? 'calendar-pan-active' : 'calendar-pan-ready') : ''"
+              >
+              <div
+                ref="calendarCanvasRef"
+                class="calendar-canvas"
+                :style="calendarCanvasStyle"
+                @wheel.prevent="onCalendarCanvasWheel"
+                @pointerdown="onCalendarCanvasPointerDown"
+                @pointermove="onCalendarCanvasPointerMove"
+                @pointerup="stopCalendarCanvasDrag"
+                @pointercancel="stopCalendarCanvasDrag"
+                @pointerleave="stopCalendarCanvasDrag"
+              >
 	            <div v-if="calendarView === 'month'" class="space-y-1">
               <div class="grid grid-cols-7 gap-1 text-center text-xs font-semibold text-base-content/60">
                 <span>Sun</span>
@@ -4217,6 +4322,7 @@ async function decideFeedCard(card: FeedCard, decision: "accepted" | "rejected")
                 <p class="mt-1 text-sm text-base-content/80">{{ event.note }}</p>
               </button>
             </div>
+              </div>
             </div>
             </div>
             </section>
@@ -5292,6 +5398,21 @@ async function decideFeedCard(card: FeedCard, decision: "accepted" | "rejected")
   height: 100%;
 }
 
+.calendar-canvas {
+  min-width: 100%;
+  transform-origin: 0 0;
+  transition: transform 120ms ease-out;
+  will-change: transform;
+}
+
+.calendar-pan-ready {
+  cursor: grab;
+}
+
+.calendar-pan-active {
+  cursor: grabbing;
+}
+
 .calendar-week-grid {
   display: grid;
   grid-template-columns: repeat(7, minmax(165px, 1fr));