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>

docs/circuit-list-editor-api.md

@@ -74,8 +74,9 @@ Protected-board structure uses
 persisted inverse of a delete. The dispatcher also supports the documented
 project-device, project settings, distribution-board and project-location
 commands. The generic editor commands listed here use schema version `1`.
-`project.update-settings` uses version `2` and still accepts supported baseline
-version `1` commands without changing the newer building classification.
+`project.update-settings` uses version `3` (including the print cover fields)
+and still accepts version `2` and supported baseline version `1` commands
+without changing the newer cover fields or building classification.
 Pre-baseline formats remain unsupported. Unsupported types or schema versions
 are rejected. Insert commands contain the complete entity or circuit block
 with stable ids; delete commands include the expected parent identity. Circuit
@@ -173,6 +174,9 @@ synchronizes linked circuit rows implicitly.
 - `PUT /projects/:projectId`
   - request:
     `{ "expectedRevision": 12, "isPublicBuilding": true, "singlePhaseVoltageV": 230, "threePhaseVoltageV": 400, "enabledDistributionBoardSupplyTypes": ["AV", "MSR", "SiBe"], ...projectMetadata }`
+  - optional print cover fields `siteAddress` (max. 500), `workStage` (max.
+    100), `projectLead` and `projectEditor` (max. 200 each); omitted fields keep
+    their value, empty strings are stored as `null`
   - executes `project.update-settings` as one atomic revision
   - response:
     `{ "project": { ... }, "revision": { ... }, "history": { ... } }`