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/furniture-id-reservation.ts

@@ -1,5 +1,5 @@
 import { sql } from "drizzle-orm";
-import { db } from "@/lib/db";
+import { queryRows } from "@/lib/db";
 import { findFurniDataIdConflict } from "./furni-data";
 
 let reservation: Promise<void> = Promise.resolve();
@@ -26,9 +26,9 @@ export async function reserveFurnitureId(
 				candidate > 2147483647
 			)
 				throw new Error("No valid furniture ID is available");
-			const [owners] = (await db.execute(
+			const owners = await queryRows<{ item_name: string }>(
 				sql`SELECT item_name FROM items_base WHERE id = ${candidate} OR sprite_id = ${candidate} LIMIT 1`,
-			)) as unknown as [Array<{ item_name: string }>, unknown];
+			);
 			const occupied =
 				owners.length > 0 ||
 				!!(await findFurniDataIdConflict(candidate, classname));
@@ -44,9 +44,9 @@ export async function reserveFurnitureId(
 						throw error;
 				}
 			}
-			const [rows] = (await db.execute(
+			const rows = await queryRows<{ maximum: number | string }>(
 				sql`SELECT GREATEST(COALESCE(MAX(id), 0), COALESCE(MAX(sprite_id), 0)) AS maximum FROM items_base`,
-			)) as unknown as [Array<{ maximum: number | string }>, unknown];
+			);
 			candidate = Math.max(candidate + 1, Number(rows[0]?.maximum ?? 0) + 1);
 		}
 		throw new Error("Cannot reserve a free furniture ID; retry the import");