feat(sprint8): Phase 4 — Dokumentenarchiv + Vorstandsverwaltung

Backend:
- V20 migration: documents table with category, access_level, file storage
- V21 migration: board_positions + board_members with term tracking
- Document entity + DocumentCategory/DocumentAccessLevel enums
- BoardPosition + BoardMember entities
- Extended AuditEventType (DOCUMENT_UPLOADED/DELETED, BOARD_MEMBER_ELECTED/REMOVED)
- Extended StaffPermission (MANAGE_DOCUMENTS)
- Extended NotificationType (BOARD_TERM_EXPIRING)
- DocumentService: upload, list, download, delete, storage usage
- BoardService: positions CRUD, elect/remove members, current/history
- DocumentController: multipart upload, filtered list, download, delete, portal
- BoardController: positions, elect, remove, current board, history, portal

Frontend:
- documents.ts + board.ts service layers
- Admin /documents page: grouped by category, upload dialog, filter, download/delete
- Admin /board page: current board cards, position management, elect member dialog
- Navigation: added Dokumente + Vorstand to sidebar
- i18n: documents.* + board.* keys in de.json + en.json

cannamanage-frontend/src/services/board.ts

@@ -0,0 +1,90 @@
+import { apiClient } from "@/lib/api-client"
+
+export interface BoardPosition {
+  id: string
+  title: string
+  description: string | null
+  sortOrder: number
+  isActive: boolean
+  createdAt: string
+}
+
+export interface BoardMember {
+  id: string
+  clubId: string
+  positionId: string
+  memberId: string
+  electedAt: string
+  termStart: string
+  termEnd: string | null
+  isCurrent: boolean
+  electedInAssemblyId: string | null
+  createdAt: string
+}
+
+export interface CreatePositionRequest {
+  title: string
+  description?: string
+  sortOrder?: number
+}
+
+export interface ElectBoardMemberRequest {
+  positionId: string
+  memberId: string
+  electedAt: string
+  termStart: string
+  termEnd?: string
+  assemblyId?: string
+}
+
+export function createPosition(
+  clubId: string,
+  data: CreatePositionRequest
+): Promise<BoardPosition> {
+  return apiClient<BoardPosition>(`/board/positions?clubId=${clubId}`, {
+    method: "POST",
+    body: data,
+  })
+}
+
+export function getPositions(clubId: string): Promise<BoardPosition[]> {
+  return apiClient<BoardPosition[]>(`/board/positions?clubId=${clubId}`)
+}
+
+export function updatePosition(
+  id: string,
+  data: Partial<CreatePositionRequest & { isActive: boolean }>
+): Promise<BoardPosition> {
+  return apiClient<BoardPosition>(`/board/positions/${id}`, {
+    method: "PUT",
+    body: data,
+  })
+}
+
+export function electBoardMember(
+  clubId: string,
+  data: ElectBoardMemberRequest
+): Promise<BoardMember> {
+  return apiClient<BoardMember>(`/board/members?clubId=${clubId}`, {
+    method: "POST",
+    body: data,
+  })
+}
+
+export function getCurrentBoard(clubId: string): Promise<BoardMember[]> {
+  return apiClient<BoardMember[]>(`/board?clubId=${clubId}`)
+}
+
+export function getBoardHistory(clubId: string): Promise<BoardMember[]> {
+  return apiClient<BoardMember[]>(`/board/history?clubId=${clubId}`)
+}
+
+export function removeBoardMember(id: string, clubId: string): Promise<void> {
+  return apiClient<void>(`/board/members/${id}?clubId=${clubId}`, {
+    method: "DELETE",
+  })
+}
+
+export function getPortalBoard(clubId: string): Promise<BoardMember[]> {
+  return apiClient<BoardMember[]>(`/portal/board?clubId=${clubId}`)
+}