Add print cover fields and office profile

- Project settings gain siteAddress, workStage, projectLead and
  projectEditor (project.update-settings schema version 3, migration 0009);
  versions 2 and 1 stay executable and keep the current cover values.
  Snapshot schema 6 carries the fields; older versions upgrade with null.
- Global office profile (office name/address) next to the document logo:
  table document_branding_settings, PUT /api/document-branding/office,
  editable from the print view toolbar.
- Cover page reads all fields; empty values show the "[ergänzen]" marker.
  The Planstände editor column shows the project editor.
- Shared logo constants moved to a dependency-free module so the Next.js
  bundler can import them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/frontend/utils/api.ts

@@ -11,6 +11,7 @@ import type {
   DistributionBoardInfoDto,
   DocumentLogoMetadataDto,
   FloorDto,
+  OfficeProfileDto,
   GlobalDeviceDto,
   ProjectCommandDto,
   ProjectCommandResultDto,
@@ -258,7 +259,7 @@ export function updateProjectSettings(
     singlePhaseVoltageV: number;
     threePhaseVoltageV: number;
     enabledDistributionBoardSupplyTypes: ProjectDto["enabledDistributionBoardSupplyTypes"];
-  }
+  } & Partial<Pick<ProjectDto, "siteAddress" | "workStage" | "projectLead" | "projectEditor">>
 ) {
   return request<ProjectSettingsCommandResultDto>(
     `/api/projects/${projectId}`,
@@ -346,9 +347,17 @@ export function updateDistributionBoard(
 export const documentLogoUrl = "/api/document-branding/logo";
 
 export function getDocumentBranding() {
-  return request<{ logo: DocumentLogoMetadataDto | null }>(
-    "/api/document-branding"
-  );
+  return request<{
+    logo: DocumentLogoMetadataDto | null;
+    office: OfficeProfileDto;
+  }>("/api/document-branding");
+}
+
+export function updateOfficeProfile(office: OfficeProfileDto) {
+  return request<{ office: OfficeProfileDto }>("/api/document-branding/office", {
+    method: "PUT",
+    body: JSON.stringify(office),
+  });
 }
 
 export async function uploadDocumentLogo(file: File) {