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>

tests/project-command.service.test.ts

@@ -1074,6 +1074,10 @@ describe("project command service", () => {
             "MSR",
             "SiBe",
           ],
+          siteAddress: null,
+          workStage: null,
+          projectLead: null,
+          projectEditor: null,
         }),
       });
       assert.equal(updated.history.currentRevision, 1);