feat: organizers, meetups UI, Plausible analytics, and migration tooling

- Add organizer model/API, admin and public organizer pages, meetup cards
- Refresh events/home/contact; add calendar dialog and carousel components
- Optional Plausible via NEXT_PUBLIC_PLAUSIBLE_* env vars in root layout
- Prisma migration, seed updates, baseline-and-migrate script

Made-with: Cursor

frontend/app/events/organizer/[slug]/page.tsx

@@ -0,0 +1,42 @@
+import type { Metadata } from "next";
+import { notFound } from "next/navigation";
+import OrganizerEventsClient from "./OrganizerEventsClient";
+import { apiUrl } from "@/lib/api-base";
+
+async function fetchOrganizer(slug: string) {
+  try {
+    const res = await fetch(apiUrl(`/organizers/by-slug/${encodeURIComponent(slug)}`), {
+      next: { revalidate: 300 },
+    });
+    if (!res.ok) return null;
+    return res.json() as Promise<{ id: string; name: string; slug: string }>;
+  } catch {
+    return null;
+  }
+}
+
+interface Props {
+  params: Promise<{ slug: string }>;
+}
+
+export async function generateMetadata({ params }: Props): Promise<Metadata> {
+  const { slug } = await params;
+  const org = await fetchOrganizer(slug);
+  if (!org) {
+    return { title: "Organizer not found" };
+  }
+  return {
+    title: `Events by ${org.name}`,
+    description: `Upcoming and past Bitcoin events organized by ${org.name} in Belgium.`,
+    alternates: { canonical: `/events/organizer/${slug}` },
+  };
+}
+
+export default async function OrganizerArchivePage({ params }: Props) {
+  const { slug } = await params;
+  const org = await fetchOrganizer(slug);
+  if (!org) {
+    notFound();
+  }
+  return <OrganizerEventsClient slug={slug} organizerName={org.name} />;
+}