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/components/public/ContactChannelGrid.tsx

@@ -0,0 +1,75 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import Link from "next/link";
+import { Send, Zap, ExternalLink } from "lucide-react";
+import { api } from "@/lib/api";
+
+const CHANNELS = [
+  {
+    key: "telegram_link" as const,
+    title: "Telegram",
+    description:
+      "Join our Telegram group for quick questions and community chat.",
+    Icon: Send,
+  },
+  {
+    key: "nostr_link" as const,
+    title: "Nostr",
+    description: "Follow us on Nostr for censorship-resistant communication.",
+    Icon: Zap,
+  },
+  {
+    key: "x_link" as const,
+    title: "X (Twitter)",
+    description: "Follow us on X for announcements and updates.",
+    Icon: ExternalLink,
+  },
+];
+
+export function ContactChannelGrid() {
+  const [settings, setSettings] = useState<Record<string, string>>({});
+
+  useEffect(() => {
+    api
+      .getPublicSettings()
+      .then((data) => setSettings(data))
+      .catch(() => {});
+  }, []);
+
+  return (
+    <div className="grid grid-cols-1 sm:grid-cols-2 gap-6">
+      {CHANNELS.map(({ key, title, description, Icon }) => {
+        const href = settings[key] || "#";
+        const isExternal = href.startsWith("http");
+        return (
+          <a
+            key={key}
+            href={href}
+            target={isExternal ? "_blank" : undefined}
+            rel={isExternal ? "noopener noreferrer" : undefined}
+            className="bg-surface-container-low p-8 rounded-xl hover:bg-surface-container transition-colors group"
+          >
+            <Icon size={28} className="text-primary mb-4" />
+            <h2 className="text-xl font-bold mb-2">{title}</h2>
+            <p className="text-on-surface-variant text-sm">{description}</p>
+          </a>
+        );
+      })}
+
+      <div className="bg-surface-container-low p-8 rounded-xl">
+        <h2 className="text-xl font-bold mb-2">Meetups</h2>
+        <p className="text-on-surface-variant text-sm mb-4">
+          The best way to connect is in person. Come to our monthly meetup in
+          Brussels.
+        </p>
+        <Link
+          href="/#meetup"
+          className="text-primary font-bold text-sm hover:underline"
+        >
+          See next meetup →
+        </Link>
+      </div>
+    </div>
+  );
+}