feat: add gated housekeeping foundation preview

src/env.ts

@@ -9,6 +9,10 @@ const schema = z
 		NODE_ENV: z
 			.enum(["development", "test", "production"])
 			.default("development"),
+		HOUSEKEEPING_NEXT_PREVIEW_ENABLED: z
+			.string()
+			.optional()
+			.transform((value) => value === "true" || value === "1"),
 		DATABASE_URL: z.string().url(),
 		DATABASE_POOL_SIZE: z.coerce.number().int().positive().default(10),
 		DATABASE_IDLE_TIMEOUT_MS: z.coerce