feat: add states CRUD API route with project-scoped workflow states

- Add states.ts with GET/POST/PATCH/DELETE endpoints
- States scoped to project via projectId FK; workspace access resolved through project
- stateGroupEnum enforced (backlog|unstarted|started|completed|cancelled)
- List ordered by sortOrder, auto-increment on create
- Soft-delete via deletedAt column (added to schema)
- 3-step contract on every write: DB write, activity feed, pg_notify
- Register /api/states route in main index.ts
- Default state seeding already present in projects.ts

packages/db/src/schema.ts

@@ -160,10 +160,12 @@ export const states = pgTable(
     sortOrder: integer('sort_order').default(0),
     createdAt: timestamp('created_at', { withTimezone: true }).defaultNow().notNull(),
     updatedAt: timestamp('updated_at', { withTimezone: true }).defaultNow().notNull(),
+    deletedAt: timestamp('deleted_at', { withTimezone: true }),
   },
   (table) => [
     index('states_project_id_idx').on(table.projectId),
     index('states_sort_order_idx').on(table.projectId, table.sortOrder),
+    index('states_deleted_at_idx').on(table.deletedAt),
   ]
 );