Add POST /category/:id/move to relocate a category.

Wires up the existing category.move store method (validates source and
target in the same company, rejects self/descendant cycles, assigns the
next sibling sort) behind an authenticated HTTP route, plus @openapi
docs and regenerated API docs.

src/db/category.js

@@ -29,3 +29,8 @@ export async function order({ googleAuthId, parentId, categoryIds }) {
     const store = await getStore();
     return store.category.order({ googleAuthId, parentId, categoryIds });
 }
+
+export async function move({ googleAuthId, id, parentId }) {
+    const store = await getStore();
+    return store.category.move({ googleAuthId, id, parentId });
+}