feat(sprint7): Phase 4 — Integration (SMTP, tier enforcement, WebSocket)

Phase 4 implementation:
- 4.1 IONOS SMTP email configuration (production + docker profiles)
- 4.2 Portal navigation update (info board, events, forum links)
- 4.3 Tier enforcement: PlanTierService (forum=Pro+, info board limits)
- 4.4 WebSocket real-time updates (WebSocketEventPublisher)
- 4.5 EmailService: notification, event reminder, info board templates + rate limiting
- 4.6 Enterprise custom FROM: CustomMailDomain entity, DNS verification, controller

New files:
- PlanTierService: tier checks for forum/info board/enterprise features
- NotificationDispatchService: EMAIL channel dispatch via preferences
- WebSocketEventPublisher: STOMP topic push for forum/info board/events
- CustomMailDomainService: DNS TXT record verification for custom FROM
- MailSettingsController: Enterprise custom domain API endpoints
- CustomMailDomain entity + repository
- V16 migration: email dispatch index
- V17 migration: custom_mail_domains table
- Frontend: use-forum-subscription + use-info-board-subscription hooks
- Portal navbar: added info board, events, forum navigation items
- i18n: added portal nav translations (de + en)

Also fixed pre-existing Phase 2.5/3 compilation issues:
- Member entity: added userId field
- AuditService: added convenience overloads (logEvent, 4-param log)
- AuditEventType: added INFO_BOARD_POST_UPDATED, INFO_BOARD_POST_DELETED
- QuotaViolationCode: added TIER_UPGRADE_REQUIRED
- StaffPermissionChecker: added requirePermission(UserDetails, ...)
- TenantContext: added getCurrentTenantId() alias
- MemberRepository: added findByUserId, findByClubId, findAllByClubId
- EmailServiceTest: updated for new constructor signature

cannamanage-frontend/src/components/portal/portal-navbar.tsx

@@ -3,7 +3,7 @@
 import Link from "next/link"
 import { usePathname } from "next/navigation"
 import { useTranslations } from "next-intl"
-import { Cannabis, History, LayoutDashboard, LogOut, User } from "lucide-react"
+import { Calendar, Cannabis, History, LayoutDashboard, LogOut, Megaphone, MessageSquare, User } from "lucide-react"
 
 import { mockPortalUser } from "@/data/mock/portal"
 
@@ -13,6 +13,9 @@ import { ModeDropdown } from "@/components/layout/mode-dropdown"
 
 const navItems = [
   { href: "/portal/dashboard", icon: LayoutDashboard, labelKey: "dashboard" },
+  { href: "/portal/info-board", icon: Megaphone, labelKey: "infoBoard" },
+  { href: "/portal/events", icon: Calendar, labelKey: "events" },
+  { href: "/portal/forum", icon: MessageSquare, labelKey: "forum" },
   { href: "/portal/history", icon: History, labelKey: "history" },
   { href: "/portal/profile", icon: User, labelKey: "profile" },
 ] as const