fix: MC series uses earliest slot date for registration cutoff

Multi-session master classes are a series — once the first session
passes, the group has started and registration closes. Changed all
MC date logic from "latest slot" / "any future slot" to "earliest slot":

- DashboardSummary: upcoming = earliest slot >= today
- McRegistrationsTab: archive = earliest slot < today
- AddBookingModal: only show MCs where earliest slot >= today
- Public MasterClasses: isUpcoming checks earliest slot

src/app/admin/bookings/AddBookingModal.tsx

@@ -42,10 +42,13 @@ export function AddBookingModal({
     adminFetch("/api/admin/sections/masterClasses").then((r) => r.json()).then((data: { items?: { title: string; slots: { date: string }[] }[] }) => {
       const today = new Date().toISOString().split("T")[0];
       const upcoming = (data.items || [])
-        .filter((mc) => mc.slots?.some((s) => s.date >= today))
+        .filter((mc) => {
+          const earliest = mc.slots?.reduce((min, s) => s.date < min ? s.date : min, mc.slots[0]?.date ?? "");
+          return earliest && earliest >= today;
+        })
         .map((mc) => ({
           title: mc.title,
-          date: mc.slots.reduce((latest, s) => s.date > latest ? s.date : latest, ""),
+          date: mc.slots.reduce((min, s) => s.date < min ? s.date : min, mc.slots[0]?.date ?? ""),
         }));
       setMcOptions(upcoming);
       if (upcoming.length === 0 && tab === "events") setEventType("open-day");

src/app/admin/bookings/McRegistrationsTab.tsx

@@ -27,17 +27,17 @@ export function McRegistrationsTab({ filter }: { filter: BookingFilter }) {
       const dates: Record<string, string> = {};
       const mcItems = mcData.items || [];
       for (const mc of mcItems) {
-        const latestSlot = mc.slots?.reduce((latest, s) => s.date > latest ? s.date : latest, "");
-        if (latestSlot) dates[mc.title] = latestSlot;
+        const earliestSlot = mc.slots?.reduce((min, s) => s.date < min ? s.date : min, mc.slots[0]?.date ?? "");
+        if (earliestSlot) dates[mc.title] = earliestSlot;
       }
       const regTitles = new Set(regData.map((r) => r.masterClassTitle));
       for (const regTitle of regTitles) {
         if (dates[regTitle]) continue;
         for (const mc of mcItems) {
-          const latestSlot = mc.slots?.reduce((latest, s) => s.date > latest ? s.date : latest, "");
-          if (!latestSlot) continue;
+          const earliestSlot = mc.slots?.reduce((min, s) => s.date < min ? s.date : min, mc.slots[0]?.date ?? "");
+          if (!earliestSlot) continue;
           if (regTitle.toLowerCase().includes(mc.title.toLowerCase()) || mc.title.toLowerCase().includes(regTitle.toLowerCase())) {
-            dates[regTitle] = latestSlot;
+            dates[regTitle] = earliestSlot;
             break;
           }
         }

src/app/admin/bookings/page.tsx

@@ -582,7 +582,8 @@ function DashboardSummary({ onNavigate }: { onNavigate: (tab: Tab) => void }) {
         // Build set of upcoming MC titles
         const upcomingTitles = new Set<string>();
         for (const mc of mcData.items || []) {
-          if (mc.slots?.some((s) => s.date >= today)) upcomingTitles.add(mc.title);
+          const earliest = mc.slots?.reduce((min, s) => s.date < min ? s.date : min, mc.slots[0]?.date ?? "");
+          if (earliest && earliest >= today) upcomingTitles.add(mc.title);
         }
         return regs.filter((r) => upcomingTitles.has(r.masterClassTitle));
       }),

src/components/sections/MasterClasses.tsx

@@ -72,16 +72,18 @@ function calcDuration(slot: MasterClassSlot): string {
 
 function isUpcoming(item: MasterClassItem): boolean {
   const now = new Date();
-  return (item.slots ?? []).some((s) => {
-    const slotDate = parseDate(s.date);
-    if (s.startTime) {
-      const [h, m] = s.startTime.split(":").map(Number);
-      slotDate.setHours(h, m, 0, 0);
-    } else {
-      slotDate.setHours(23, 59, 59, 999);
-    }
-    return slotDate > now;
-  });
+  const slots = item.slots ?? [];
+  if (slots.length === 0) return false;
+  // Series MC: check earliest slot — if first session passed, group already started
+  const earliestSlot = slots.reduce((min, s) => s.date < min.date ? s : min, slots[0]);
+  const d = parseDate(earliestSlot.date);
+  if (earliestSlot.startTime) {
+    const [h, m] = earliestSlot.startTime.split(":").map(Number);
+    d.setHours(h, m, 0, 0);
+  } else {
+    d.setHours(23, 59, 59, 999);
+  }
+  return d > now;
 }
 
 function MasterClassCard({