feat(FN-3626): migrate plugin storage to project-scoped storage

Migrated the dependency-graph plugin's storage layer to use the project's scoped storage API (`projectStorage`) and added canonical storage-key assertions. The ChatView.tsx utility reference was updated to match the new storage path.

Fusion-Task-Id: FN-3626

packages/dashboard/app/utils/__tests__/projectStorage.test.ts

@@ -96,9 +96,10 @@ describe("projectStorage", () => {
         "kb-usage-provider-order",
         "kb-chat-active-session",
         "kb-files-line-numbers",
+        "fusion-plugin-dependency-graph:positions",
       ]),
     );
-    expect(PROJECT_STORAGE_KEYS).toHaveLength(20);
+    expect(PROJECT_STORAGE_KEYS).toHaveLength(21);
   });
 
   it("has no overlap between global and project-scoped keys", () => {