feat: add complex user invitation and management features

- Implemented complex member and invitation schemas using Zod for validation.
- Created new API endpoints for inviting, accepting, revoking, and canceling complex user invitations.
- Developed handlers for managing complex users, including listing, inviting, revoking, and canceling invitations.
- Added frontend components for displaying and managing complex users and invitations.
- Introduced session storage management for pending invitations.
- Integrated Gravatar for user avatars based on email.
- Created database migration for complex invitations table.

apps/backend/prisma/complex.prisma

@@ -12,6 +12,7 @@ model Complex {
   updatedAt       DateTime      @updatedAt @map("updated_at")
   plan            Plan?         @relation(fields: [planCode], references: [code])
   users           ComplexUser[]
+  invitations     ComplexInvitation[]
   courts          Court[]
 
   @@index([planCode])
@@ -36,3 +37,20 @@ model ComplexUser {
   @@index([userId])
   @@map("complex_users")
 }
+
+model ComplexInvitation {
+  id         String   @id @db.Uuid
+  complexId   String   @map("complex_id") @db.Uuid
+  email       String   @db.VarChar(255)
+  tokenHash   String   @unique @map("token_hash")
+  expiresAt   DateTime @map("expires_at")
+  acceptedAt  DateTime? @map("accepted_at")
+  revokedAt   DateTime? @map("revoked_at")
+  createdAt   DateTime @default(now()) @map("created_at")
+  updatedAt   DateTime @updatedAt @map("updated_at")
+  complex     Complex  @relation(fields: [complexId], references: [id], onDelete: Cascade)
+
+  @@index([complexId, email])
+  @@index([email])
+  @@map("complex_invitations")
+}

apps/backend/prisma/migrations/20260422120000_add_complex_invitations/migration.sql

@@ -0,0 +1,26 @@
+-- CreateTable
+CREATE TABLE "complex_invitations" (
+    "id" UUID NOT NULL,
+    "complex_id" UUID NOT NULL,
+    "email" VARCHAR(255) NOT NULL,
+    "token_hash" TEXT NOT NULL,
+    "expires_at" TIMESTAMP(3) NOT NULL,
+    "accepted_at" TIMESTAMP(3),
+    "revoked_at" TIMESTAMP(3),
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "complex_invitations_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "complex_invitations_token_hash_key" ON "complex_invitations"("token_hash");
+
+-- CreateIndex
+CREATE INDEX "complex_invitations_complex_id_email_idx" ON "complex_invitations"("complex_id", "email");
+
+-- CreateIndex
+CREATE INDEX "complex_invitations_email_idx" ON "complex_invitations"("email");
+
+-- AddForeignKey
+ALTER TABLE "complex_invitations" ADD CONSTRAINT "complex_invitations_complex_id_fkey" FOREIGN KEY ("complex_id") REFERENCES "complexes"("id") ON DELETE CASCADE ON UPDATE CASCADE;