feat: member portal Sprint 2 — digest history page and restore Digest/DigestConfig schema models

- Restore Digest + DigestConfig models to schema.prisma (wiped by prior git reset)
- Add Tenant.digestConfig / Tenant.digests relations
- GET /my/digest API endpoint (last 20 digests, truncated summary)
- BFF route /api/my/digest
- /my/digest page: digest cards with date, message count, summary preview
- Add Digest nav item to MemberShell sidebar

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

apps/api/src/modules/my/my.controller.ts

@@ -29,6 +29,11 @@ export class MyController {
     return this.service.getDashboard(member.sub, member.tenantId);
   }
 
+  @Get('digest')
+  digests(@CurrentMember() member: MemberJwtPayload) {
+    return this.service.getDigests(member.tenantId);
+  }
+
   @Get('profile')
   profile(@CurrentMember() member: MemberJwtPayload) {
     return this.service.getProfile(member.sub, member.tenantId);