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/schema.prisma

@@ -17,8 +17,17 @@ model User {
   updatedAt   DateTime @updatedAt
 }
 
+model Organizer {
+  id        String   @id @default(uuid())
+  name      String
+  slug      String   @unique
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+  meetups   Meetup[]
+}
+
 model Meetup {
-  id          String   @id @default(uuid())
+  id          String    @id @default(uuid())
   title       String
   description String
   date        String
@@ -26,11 +35,13 @@ model Meetup {
   location    String
   link        String?
   imageId     String?
-  status      String   @default("DRAFT") // DRAFT, PUBLISHED, CANCELLED (Upcoming/Past derived from date)
-  featured    Boolean  @default(false)
-  visibility  String   @default("PUBLIC") // PUBLIC, HIDDEN
-  createdAt   DateTime @default(now())
-  updatedAt   DateTime @updatedAt
+  status      String    @default("DRAFT") // DRAFT, PUBLISHED, CANCELLED (Upcoming/Past derived from date)
+  featured    Boolean   @default(false)
+  visibility  String    @default("PUBLIC") // PUBLIC, HIDDEN
+  organizerId String
+  organizer   Organizer @relation(fields: [organizerId], references: [id], onDelete: Restrict)
+  createdAt   DateTime  @default(now())
+  updatedAt   DateTime  @updatedAt
 }
 
 model Media {