feat(FN-3990): add task lineage identity and association storage

Adds task lineage storage infrastructure (FN-3990 Step 2), introducing a dedicated `task-lineage.ts` module and related types to track task identity and association relationships, with corresponding database schema and store support plus tests and documentation for the lineage reconciliation process

Fusion-Task-Id: FN-3990

plugins/fusion-plugin-roadmap/src/store/__tests__/roadmap-store.test.ts

@@ -744,7 +744,7 @@ describe("RoadmapStore", () => {
 
   describe("schema version", () => {
     it("schema version is 40 after init", () => {
-      expect(db.getSchemaVersion()).toBe(71);
+      expect(db.getSchemaVersion()).toBe(72);
     });
   });