feat(folders): add resource pinning and generalize the folders contract (#6014)

- Adds per-user pinning for workflows, files, knowledge bases, and tables: new `pinned_item` table, `/api/pinned-items` routes, React Query hooks, and a shared `PinButton` wired into Tables, Knowledge, and Files with pinned-first ordering
- Adds the generic `folder` table with an idempotent, replay-safe, collision-aware backfill from `workflow_folder` and `workspace_file_folders`; no cutover yet, folder reads still go through a documented legacy adapter
- Moves `folderSchema` to the generic vocabulary (`resourceType`, `deletedAt`) and drops the unused `color`/`isExpanded`

packages/testing/src/mocks/schema.mock.ts

@@ -68,6 +68,27 @@ export const schemaMock = {
     createdAt: 'createdAt',
     updatedAt: 'updatedAt',
   },
+  folder: {
+    id: 'id',
+    resourceType: 'resourceType',
+    name: 'name',
+    userId: 'userId',
+    workspaceId: 'workspaceId',
+    parentId: 'parentId',
+    locked: 'locked',
+    sortOrder: 'sortOrder',
+    createdAt: 'createdAt',
+    updatedAt: 'updatedAt',
+    deletedAt: 'deletedAt',
+  },
+  pinnedItem: {
+    id: 'id',
+    userId: 'userId',
+    workspaceId: 'workspaceId',
+    resourceType: 'resourceType',
+    resourceId: 'resourceId',
+    pinnedAt: 'pinnedAt',
+  },
   workflowFolder: {
     id: 'id',
     name: 'name',