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/actions/admin-table-views.test.ts

@@ -23,13 +23,15 @@ vi.mock("@/lib/report-error", () => ({ reportError: vi.fn() }));
 vi.mock("@/lib/foundation/security", () => ({
 	extractClientIpAsync: async () => "127.0.0.1",
 }));
-vi.mock("@/lib/db", () => {
+vi.mock("@/lib/db", async () => {
+	const { createDbHelpers } = await import("@/test/db-helpers");
 	const execute = async (sql: SQL) => {
 		const query = new MySqlDialect().sqlToQuery(sql);
 		state.queries.push(query);
 		return [state.rows];
 	};
 	return {
+		...createDbHelpers(execute),
 		db: {
 			execute,
 			transaction: async (fn: (tx: { execute: typeof execute }) => unknown) =>