refactor(db): typed query helpers, shared test FormData helper

Replace raw db.execute tuple casts with queryRows/rowsFrom/execResult/
affectedRows helpers from lib/db, drop redundant mysql2 casts on typed
query builders, and centralize per-test fakeForm into test/fake-form.
Update db mocks in tests so helpers resolve against mocked execute.

src/lib/services/catalog-tree.ts

@@ -3,7 +3,7 @@ import {
 	deletePageCommand,
 	updatePageCommand,
 } from "@/features/catalog/server/page-commands";
-import { CatalogPages, db } from "@/lib/db";
+import { CatalogPages, db, queryRows } from "@/lib/db";
 
 export type { NestedTreeNode, TreeNode } from "@/types/catalog";
 
@@ -29,27 +29,27 @@ export async function getCatalogItemCounts(
 
 		if (pageIds) {
 			const idStrs = pageIds.map(String);
-			const [rows] = (await db.execute(sql`
+			const rows = await queryRows<{
+				page_id: string | number;
+				cnt: number | bigint;
+			}>(sql`
 				SELECT page_id, COUNT(*) as cnt
 				FROM catalog_items
 				WHERE page_id IN (${sql.join(idStrs, sql`, `)})
 				GROUP BY page_id
-			`)) as unknown as [
-				{ page_id: string | number; cnt: number | bigint }[],
-				unknown[],
-			];
+			`);
 			for (const r of rows) {
 				map.set(toInt(r.page_id), toInt(r.cnt));
 			}
 			return map;
 		}
 
-		const [rows] = (await db.execute(sql`
+		const rows = await queryRows<{
+			page_id: string | number;
+			cnt: number | bigint;
+		}>(sql`
 			SELECT page_id, COUNT(*) as cnt FROM catalog_items GROUP BY page_id
-		`)) as unknown as [
-			{ page_id: string | number; cnt: number | bigint }[],
-			unknown[],
-		];
+		`);
 		for (const r of rows) {
 			map.set(toInt(r.page_id), toInt(r.cnt));
 		}