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/scripts/baseline-and-migrate.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+# Use when `npm run db:migrate` fails with P3005 (DB has tables but no migrate history, e.g. after db push).
+# Marks historical migrations as already applied, then runs `migrate deploy` to apply pending ones (e.g. organizer).
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+for migration_name in \
+  20260331051150_add_user_username \
+  20260331053518_add_meetup_visibility \
+  20260331061812_add_user_username
+do
+  echo "Marking as applied: $migration_name"
+  # Ignore failures when already recorded or already baselined
+  dotenv -e ../.env -e .env -- prisma migrate resolve --applied "$migration_name" || true
+done
+
+echo "Applying any pending migrations..."
+dotenv -e ../.env -e .env -- prisma migrate deploy