feat: member portal Sprint 7 — Circles (interest/affinity sub-groups)

- Circle + CircleMembership models + migration (CircleRole: MEMBER/LEAD, public/invite-only)
- CirclesModule: admin CRUD + member list; unique circle name per tenant
- Member endpoints in MyController: GET /my/circles, POST /my/circles/:id/join|leave
- listForMember returns public circles + private ones the member belongs to, with isMember/myRole/memberCount
- join() enforces invite-only; leave() removes membership
- /my/circles page: "My circles" + "Discover" split, join/leave button, LEAD + Private badges
- Member + admin BFF routes; Circles nav item
- Register CirclesModule; add CIRCLE_CREATED/DELETED audit actions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/prisma/migrations/20260617230000_add_circles/migration.sql

@@ -0,0 +1,31 @@
+CREATE TYPE "CircleRole" AS ENUM ('MEMBER', 'LEAD');
+
+CREATE TABLE "Circle" (
+    "id" TEXT NOT NULL,
+    "tenantId" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "description" TEXT,
+    "isPublic" BOOLEAN NOT NULL DEFAULT true,
+    "createdBy" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+    CONSTRAINT "Circle_pkey" PRIMARY KEY ("id")
+);
+
+CREATE TABLE "CircleMembership" (
+    "id" TEXT NOT NULL,
+    "circleId" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "role" "CircleRole" NOT NULL DEFAULT 'MEMBER',
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "CircleMembership_pkey" PRIMARY KEY ("id")
+);
+
+CREATE UNIQUE INDEX "Circle_tenantId_name_key" ON "Circle"("tenantId", "name");
+CREATE INDEX "Circle_tenantId_isPublic_idx" ON "Circle"("tenantId", "isPublic");
+CREATE UNIQUE INDEX "CircleMembership_circleId_userId_key" ON "CircleMembership"("circleId", "userId");
+CREATE INDEX "CircleMembership_userId_idx" ON "CircleMembership"("userId");
+
+ALTER TABLE "Circle" ADD CONSTRAINT "Circle_tenantId_fkey" FOREIGN KEY ("tenantId") REFERENCES "Tenant"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
+ALTER TABLE "CircleMembership" ADD CONSTRAINT "CircleMembership_circleId_fkey" FOREIGN KEY ("circleId") REFERENCES "Circle"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "CircleMembership" ADD CONSTRAINT "CircleMembership_userId_fkey" FOREIGN KEY ("userId") REFERENCES "TowerUser"("id") ON DELETE RESTRICT ON UPDATE CASCADE;

apps/api/prisma/schema.prisma

@@ -94,6 +94,7 @@ model Tenant {
   threads        Thread[]
   sevaOpportunities  SevaOpportunity[]
   gamificationEvents GamificationEvent[]
+  circles            Circle[]
 }
 
 enum AdminRole {
@@ -420,6 +421,7 @@ model TowerUser {
   rsvps    EventRsvp[]
   sevaEntries        SevaEntry[]
   gamificationEvents GamificationEvent[]
+  circleMemberships  CircleMembership[]
 
   @@unique([tenantId, phoneHash])
   @@index([phoneHash])
@@ -689,3 +691,42 @@ model GamificationEvent {
   // One award per (user, type, ref) — prevents double-awarding the same source.
   @@unique([userId, type, refId])
 }
+
+// ============================================================================
+// Circles (interest / affinity sub-groups within a chapter)
+// ============================================================================
+
+enum CircleRole {
+  MEMBER
+  LEAD
+}
+
+model Circle {
+  id          String   @id @default(cuid())
+  tenantId    String
+  tenant      Tenant   @relation(fields: [tenantId], references: [id])
+  name        String
+  description String?
+  isPublic    Boolean  @default(true)
+  createdBy   String
+  createdAt   DateTime @default(now())
+  updatedAt   DateTime @updatedAt
+
+  memberships CircleMembership[]
+
+  @@unique([tenantId, name])
+  @@index([tenantId, isPublic])
+}
+
+model CircleMembership {
+  id        String     @id @default(cuid())
+  circleId  String
+  circle    Circle     @relation(fields: [circleId], references: [id], onDelete: Cascade)
+  userId    String
+  user      TowerUser  @relation(fields: [userId], references: [id])
+  role      CircleRole @default(MEMBER)
+  createdAt DateTime   @default(now())
+
+  @@unique([circleId, userId])
+  @@index([userId])
+}