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

backend/prisma/migrations/20260403120000_add_organizer/migration.sql

@@ -0,0 +1,47 @@
+-- CreateTable
+CREATE TABLE "Organizer" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "name" TEXT NOT NULL,
+    "slug" TEXT NOT NULL,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" DATETIME NOT NULL
+);
+
+CREATE UNIQUE INDEX "Organizer_slug_key" ON "Organizer"("slug");
+
+INSERT INTO "Organizer" ("id", "name", "slug", "createdAt", "updatedAt")
+VALUES (
+    '00000000-0000-4000-8000-000000000001',
+    'Belgian Bitcoin Embassy',
+    'belgian-bitcoin-embassy',
+    datetime('now'),
+    datetime('now')
+);
+
+-- RedefineTables
+PRAGMA defer_foreign_keys=ON;
+PRAGMA foreign_keys=OFF;
+CREATE TABLE "new_Meetup" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "title" TEXT NOT NULL,
+    "description" TEXT NOT NULL,
+    "date" TEXT NOT NULL,
+    "time" TEXT NOT NULL,
+    "location" TEXT NOT NULL,
+    "link" TEXT,
+    "imageId" TEXT,
+    "status" TEXT NOT NULL DEFAULT 'DRAFT',
+    "featured" BOOLEAN NOT NULL DEFAULT false,
+    "visibility" TEXT NOT NULL DEFAULT 'PUBLIC',
+    "organizerId" TEXT NOT NULL,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" DATETIME NOT NULL,
+    CONSTRAINT "Meetup_organizerId_fkey" FOREIGN KEY ("organizerId") REFERENCES "Organizer" ("id") ON DELETE RESTRICT ON UPDATE CASCADE
+);
+INSERT INTO "new_Meetup" ("createdAt", "date", "description", "featured", "id", "imageId", "link", "location", "organizerId", "status", "time", "title", "updatedAt", "visibility")
+SELECT "createdAt", "date", "description", "featured", "id", "imageId", "link", "location", '00000000-0000-4000-8000-000000000001', "status", "time", "title", "updatedAt", "visibility" FROM "Meetup";
+DROP TABLE "Meetup";
+ALTER TABLE "new_Meetup" RENAME TO "Meetup";
+CREATE INDEX "Meetup_organizerId_idx" ON "Meetup"("organizerId");
+PRAGMA foreign_keys=ON;
+PRAGMA defer_foreign_keys=OFF;