Add optional room areas

tests/project-state-snapshot.test.ts

@@ -91,7 +91,14 @@ function minimalSnapshot() {
       sortOrder: number;
       buildingId: string | null;
     }>,
-    rooms: [],
+    rooms: [] as Array<{
+      id: string;
+      projectId: string;
+      floorId: string | null;
+      roomNumber: string;
+      roomName: string;
+      areaM2: number | null;
+    }>,
   };
 }
 
@@ -443,6 +450,26 @@ describe("project state snapshot model", () => {
     assert.throws(() => parseProjectStateSnapshot(floorWithoutBuildingField));
   });
 
+  it("keeps room areas and upgrades snapshot version 7 with an empty area", () => {
+    const current = minimalSnapshot();
+    current.rooms.push({
+      id: "room-1",
+      projectId: "project-1",
+      floorId: null,
+      roomNumber: "001",
+      roomName: "Technik",
+      areaM2: 23.456,
+    });
+    assert.equal(parseProjectStateSnapshot(current).rooms[0]?.areaM2, 23.456);
+
+    const previous = structuredClone(current);
+    previous.schemaVersion = 7 as typeof previous.schemaVersion;
+    delete (previous.rooms[0] as Partial<(typeof previous.rooms)[number]>).areaM2;
+    const upgraded = parseProjectStateSnapshot(previous);
+    assert.equal(upgraded.schemaVersion, projectStateSnapshotSchemaVersion);
+    assert.equal(upgraded.rooms[0]?.areaM2, null);
+  });
+
   it("upgrades snapshot version 6 without buildings", () => {
     const snapshot = minimalSnapshot();
     snapshot.floors.push({