feat: add reminders tab with status tracking (coming/pending/cancelled)

Auto-surfaces bookings for today and tomorrow. Admin sets status per
person: coming, no answer, or cancelled. Summary stats per day.
DB migration 8 adds reminder_status column to all booking tables.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/app/api/admin/reminders/route.ts

@@ -0,0 +1,36 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getUpcomingReminders, setReminderStatus } from "@/lib/db";
+import type { ReminderStatus } from "@/lib/db";
+
+export async function GET() {
+  return NextResponse.json(getUpcomingReminders());
+}
+
+export async function PUT(request: NextRequest) {
+  try {
+    const body = await request.json();
+    const { table, id, status } = body;
+
+    const validTables = ["mc_registrations", "group_bookings", "open_day_bookings"];
+    const validStatuses = ["pending", "coming", "cancelled", null];
+
+    if (!validTables.includes(table)) {
+      return NextResponse.json({ error: "Invalid table" }, { status: 400 });
+    }
+    if (!id || typeof id !== "number") {
+      return NextResponse.json({ error: "id is required" }, { status: 400 });
+    }
+    if (!validStatuses.includes(status)) {
+      return NextResponse.json({ error: "Invalid status" }, { status: 400 });
+    }
+
+    setReminderStatus(
+      table as "mc_registrations" | "group_bookings" | "open_day_bookings",
+      id,
+      status as ReminderStatus | null
+    );
+    return NextResponse.json({ ok: true });
+  } catch {
+    return NextResponse.json({ error: "Internal error" }, { status: 500 });
+  }
+}