Add buildings above floors and a building structure page

Projects with several buildings could not be structured: floors and rooms
hung directly off the project. Floors can now belong to a building
(migration 0009: table buildings, nullable floors.building_id). Rooms and
distribution boards keep their floor; their building follows from it.
Existing floors stay without a building.

Buildings use the location-structure command store with
project-building.insert/.update/.delete, inverses and persistent Undo/Redo;
deleting a building with assigned floors is rejected. Floor commands carry
buildingId since command version 2. Version 1 floor commands from existing
history predate buildings and are upgraded with buildingId = null before
they are executed and persisted, so forward and inverse keep one version.

Project snapshot schema 7 stores buildings and floor.buildingId; versions
1-6 are upgraded without buildings. Restore and portable transfer include
buildings, and the transfer remaps building ids.

Buildings, floors and rooms move from the project overview to their own
page /projects/:id/struktur with three columns (Gebäude -> Etagen -> Räume)
that filter each other, and a sidebar entry. Floor selects in the board and
room dialogs are grouped by building. Unchanged dialogs close without a
command. Details in docs/building-structure.md; see issue #6.

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

tests/project-state-snapshot.test.ts

@@ -8,10 +8,22 @@ import {
 } from "../src/domain/models/project-state-snapshot.model.js";
 import { createNamedProjectSnapshotSchema } from "../src/shared/validation/project-snapshot.schemas.js";
 
-/** Removes the fields introduced by snapshot schema version 6. */
-function withoutVersionSixFields<
-  T extends { project: object; distributionBoards: object[] },
+/** Removes the fields introduced by snapshot schema version 7. */
+function withoutVersionSevenFields<
+  T extends { floors: object[] },
 >(snapshot: T): T {
+  delete (snapshot as Record<string, unknown>).buildings;
+  for (const floor of snapshot.floors) {
+    delete (floor as Record<string, unknown>).buildingId;
+  }
+  return snapshot;
+}
+
+/** Removes the fields introduced by snapshot schema versions 6 and 7. */
+function withoutVersionSixFields<
+  T extends { project: object; distributionBoards: object[]; floors: object[] },
+>(snapshot: T): T {
+  withoutVersionSevenFields(snapshot);
   const project = snapshot.project as Record<string, unknown>;
   for (const field of ["siteAddress", "workStage", "projectLead", "projectEditor"]) {
     delete project[field];
@@ -66,7 +78,19 @@ function minimalSnapshot() {
     distributionBoardComponentProtectionDevices: [],
     circuits: [],
     projectDevices: [],
-    floors: [],
+    buildings: [] as Array<{
+      id: string;
+      projectId: string;
+      name: string;
+      sortOrder: number;
+    }>,
+    floors: [] as Array<{
+      id: string;
+      projectId: string;
+      name: string;
+      sortOrder: number;
+      buildingId: string | null;
+    }>,
     rooms: [],
   };
 }
@@ -306,7 +330,10 @@ describe("project state snapshot model", () => {
     delete (outdated.project as Record<string, unknown>).description;
     assert.throws(() => parseProjectStateSnapshot(outdated));
     assert.throws(() =>
-      parseProjectStateSnapshot({ ...minimalSnapshot(), schemaVersion: 7 })
+      parseProjectStateSnapshot({
+        ...minimalSnapshot(),
+        schemaVersion: projectStateSnapshotSchemaVersion + 1,
+      })
     );
   });
 
@@ -355,12 +382,99 @@ describe("project state snapshot model", () => {
       projectId: "project-2",
       name: "EG",
       sortOrder: 10,
+      buildingId: null,
     });
     assert.throws(
       () => parseProjectStateSnapshot(wrongOwner),
       /floor belongs to a different project/
     );
   });
+
+  it("keeps buildings and validates floor building references", () => {
+    const snapshot = minimalSnapshot();
+    snapshot.buildings.push({
+      id: "building-1",
+      projectId: "project-1",
+      name: "Haus A",
+      sortOrder: 0,
+    });
+    snapshot.floors.push(
+      {
+        id: "floor-1",
+        projectId: "project-1",
+        name: "EG",
+        sortOrder: 0,
+        buildingId: "building-1",
+      },
+      {
+        id: "floor-2",
+        projectId: "project-1",
+        name: "Keller",
+        sortOrder: 1,
+        buildingId: null,
+      }
+    );
+    const parsed = deserializeProjectStateSnapshot(
+      serializeProjectStateSnapshot(parseProjectStateSnapshot(snapshot))
+    );
+    assert.deepEqual(parsed.buildings, snapshot.buildings);
+    assert.deepEqual(
+      parsed.floors.map((floor) => floor.buildingId),
+      ["building-1", null]
+    );
+
+    const unknownBuilding = structuredClone(snapshot);
+    unknownBuilding.floors[0]!.buildingId = "building-x";
+    assert.throws(
+      () => parseProjectStateSnapshot(unknownBuilding),
+      /floor building/
+    );
+
+    const foreignBuilding = structuredClone(snapshot);
+    foreignBuilding.buildings[0]!.projectId = "project-2";
+    assert.throws(
+      () => parseProjectStateSnapshot(foreignBuilding),
+      /building belongs to a different project/
+    );
+
+    const floorWithoutBuildingField = structuredClone(snapshot);
+    delete (floorWithoutBuildingField.floors[1] as Record<string, unknown>)
+      .buildingId;
+    assert.throws(() => parseProjectStateSnapshot(floorWithoutBuildingField));
+  });
+
+  it("upgrades snapshot version 6 without buildings", () => {
+    const snapshot = minimalSnapshot();
+    snapshot.floors.push({
+      id: "floor-1",
+      projectId: "project-1",
+      name: "EG",
+      sortOrder: 0,
+      buildingId: null,
+    });
+    const previous = withoutVersionSevenFields(structuredClone(snapshot));
+    previous.schemaVersion = 6 as typeof previous.schemaVersion;
+
+    const upgraded = parseProjectStateSnapshot(previous);
+
+    assert.equal(upgraded.schemaVersion, projectStateSnapshotSchemaVersion);
+    assert.deepEqual(upgraded.buildings, []);
+    assert.deepEqual(upgraded.floors, [
+      {
+        id: "floor-1",
+        projectId: "project-1",
+        name: "EG",
+        sortOrder: 0,
+        buildingId: null,
+      },
+    ]);
+    // Version 6 cover values survive the upgrade.
+    assert.equal(upgraded.project.workStage, "LPH 5");
+
+    const mislabeled = structuredClone(snapshot);
+    mislabeled.schemaVersion = 6 as typeof mislabeled.schemaVersion;
+    assert.throws(() => parseProjectStateSnapshot(mislabeled));
+  });
 });
 
 describe("named project snapshot request", () => {