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-domain/src/main/java/de/cannamanage/domain/entity/CustomMailDomain.java

@@ -0,0 +1,51 @@
+package de.cannamanage.domain.entity;
+
+import jakarta.persistence.*;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.time.Instant;
+import java.util.UUID;
+
+/**
+ * Stores custom mail domain configuration for Enterprise tier clubs.
+ * Verified via DNS TXT record: cannamanage-verify={verification_token}
+ */
+@Data
+@NoArgsConstructor
+@Entity
+@Table(name = "custom_mail_domains")
+public class CustomMailDomain {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private UUID id;
+
+    @Column(name = "tenant_id", nullable = false, unique = true)
+    private UUID tenantId;
+
+    @Column(name = "from_address", nullable = false)
+    private String fromAddress;
+
+    @Column(name = "domain", nullable = false)
+    private String domain;
+
+    @Column(name = "verification_token", nullable = false, length = 64)
+    private String verificationToken;
+
+    @Column(name = "verified", nullable = false)
+    private boolean verified = false;
+
+    @Column(name = "verified_at")
+    private Instant verifiedAt;
+
+    @Column(name = "created_at", nullable = false)
+    private Instant createdAt = Instant.now();
+
+    public CustomMailDomain(UUID tenantId, String fromAddress, String domain, String verificationToken) {
+        this.tenantId = tenantId;
+        this.fromAddress = fromAddress;
+        this.domain = domain;
+        this.verificationToken = verificationToken;
+    }
+}

cannamanage-domain/src/main/java/de/cannamanage/domain/entity/Member.java

@@ -15,6 +15,9 @@ import java.util.UUID;
 )
 public class Member extends AbstractTenantEntity {
 
+    @Column(name = "user_id")
+    private UUID userId;
+
     @Column(name = "club_id", nullable = false)
     private UUID clubId;
 
@@ -46,6 +49,9 @@ public class Member extends AbstractTenantEntity {
     @Column(name = "prevention_officer", nullable = false)
     private boolean preventionOfficer = false;
 
+    public UUID getUserId() { return userId; }
+    public void setUserId(UUID userId) { this.userId = userId; }
+
     public UUID getClubId() { return clubId; }
     public void setClubId(UUID clubId) { this.clubId = clubId; }
 

cannamanage-domain/src/main/java/de/cannamanage/domain/entity/TenantContext.java

@@ -17,6 +17,11 @@ public final class TenantContext {
         return CURRENT_TENANT.get();
     }
 
+    /** Alias for getCurrentTenant() — used by controllers expecting this name. */
+    public static UUID getCurrentTenantId() {
+        return CURRENT_TENANT.get();
+    }
+
     public static void setCurrentTenant(UUID tenantId) {
         CURRENT_TENANT.set(tenantId);
     }

cannamanage-domain/src/main/java/de/cannamanage/domain/enums/AuditEventType.java

@@ -48,8 +48,10 @@ public enum AuditEventType {
     // Sprint 7 — Info Board events
     INFO_BOARD_POST_CREATED,
     INFO_BOARD_POST_EDITED,
+    INFO_BOARD_POST_UPDATED,
     INFO_BOARD_POST_PINNED,
     INFO_BOARD_POST_ARCHIVED,
+    INFO_BOARD_POST_DELETED,
 
     // Sprint 7 — Event Calendar events
     EVENT_CREATED,