feat(sprint8): Phase 3 — Mitgliederversammlung (assemblies, voting, protocol PDF)

Backend:
- V19 migration: assemblies, assembly_agenda_items, assembly_attendees, assembly_votes, assembly_vote_records
- Enums: AssemblyType, AssemblyStatus, AgendaItemType, VoteType, VoteDecision, VoteResult
- Entities: Assembly, AssemblyAgendaItem, AssemblyAttendee, AssemblyVote, AssemblyVoteRecord
- Repositories: Assembly, AgendaItem, Attendee, Vote, VoteRecord
- AssemblyService: full lifecycle (create, invite, start, attend, vote, quorum, complete)
- AssemblyProtocolService: OpenPDF protocol generation (§147 AO compliant)
- AssemblyController: admin + portal endpoints
- Extended: AuditEventType, NotificationType, StaffPermission

Frontend:
- Assembly service with full API client and TypeScript types
- Admin assemblies list page with create dialog (agenda builder)
- Admin assembly detail page (quorum, agenda, votes, attendees)
- Navigation: Versammlungen with Gavel icon (after Finanzen)

Legal basis: §32-§40 BGB (Mitgliederversammlung), §147 AO (retention)

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

@@ -3,7 +3,16 @@
 import Link from "next/link"
 import { usePathname } from "next/navigation"
 import { useTranslations } from "next-intl"
-import { Calendar, Cannabis, History, LayoutDashboard, LogOut, Megaphone, MessageSquare, User } from "lucide-react"
+import {
+  Calendar,
+  Cannabis,
+  History,
+  LayoutDashboard,
+  LogOut,
+  Megaphone,
+  MessageSquare,
+  User,
+} from "lucide-react"
 
 import { mockPortalUser } from "@/data/mock/portal"