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/bearer-route-abilities.test.ts

@@ -5,6 +5,7 @@ const state = vi.hoisted(() => ({
 	queries: [] as string[],
 }));
 vi.mock("@/lib/db", async () => {
+	const { createDbHelpers } = await import("@/test/db-helpers");
 	const schema = await import("@/db/schema");
 	const { drizzle } = await import("drizzle-orm/mysql-proxy");
 	const db = drizzle(async (sql) => {
@@ -27,9 +28,13 @@ vi.mock("@/lib/db", async () => {
 		}
 		return { rows: [] };
 	});
+	const mockDb = Object.assign(db, {
+		execute: async () => [[{ cnt: 0n }], []],
+	});
 	return {
 		...schema,
-		db: Object.assign(db, { execute: async () => [[{ cnt: 0n }], []] }),
+		...createDbHelpers(mockDb.execute),
+		db: mockDb,
 	};
 });
 vi.mock("@/lib/auth", () => ({ auth: async () => ({ user: { id: "77" } }) }));