feat(activities): editable stages with tab and kanban views

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/prisma/schema.prisma

@@ -206,6 +206,7 @@ model Organization {
   reservationAppointments ReservationAppointment[]
   leads                  Lead[]
   leadStages             LeadStage[]
+  activityStages         ActivityStage[]
   leadEvents             LeadEvent[]
   leadImportJobs         LeadImportJob[]
   conversationSettings   ConversationSettings?
@@ -628,6 +629,23 @@ model Deal {
   @@index([organizationId, sourceRef])
 }
 
+/// مراحل/ستون‌های فعالیت (تب و کانبان) — kind وضعیت فعالیت داخل این مرحله را تعیین می‌کند
+model ActivityStage {
+  id             String         @id @default(cuid())
+  organizationId String
+  organization   Organization   @relation(fields: [organizationId], references: [id], onDelete: Cascade)
+  name           String
+  position       Int            @default(0)
+  color          String         @default("green")
+  kind           ActivityStatus @default(open)
+  activities     Activity[]
+  createdAt      DateTime       @default(now())
+  updatedAt      DateTime       @updatedAt
+
+  @@unique([organizationId, name])
+  @@index([organizationId, position])
+}
+
 model Activity {
   id             String         @id @default(cuid())
   organizationId String
@@ -662,9 +680,13 @@ model Activity {
   createdBy      User?          @relation("ActivityCreator", fields: [createdById], references: [id], onDelete: SetNull)
   notes          Note[]
   routineTasks   RoutineTask[]
+  /// مرحله (ستون کانبان)؛ null یا مرحلهٔ ناهم‌نوع با status → اولین مرحلهٔ هم‌نوع
+  stageId        String?
+  stage          ActivityStage? @relation(fields: [stageId], references: [id], onDelete: SetNull)
   createdAt      DateTime       @default(now())
   updatedAt      DateTime       @updatedAt
 
+  @@index([stageId])
   @@index([organizationId, status, dueAt])
   @@index([organizationId, assigneeId])
   @@index([organizationId, createdById])