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/web/app/my/layout.tsx

@@ -7,6 +7,7 @@ const NAV = [
   { href: '/my/digest', label: 'Digest' },
   { href: '/my/events', label: 'Events' },
   { href: '/my/seva', label: 'Seva & Points' },
+  { href: '/my/circles', label: 'Circles' },
   { href: '/my/groups', label: 'My Groups' },
   { href: '/my/settings', label: 'Settings' },
 ];