feat: add Auto Check MH Payment toggle with weekly schedule

Adds a toggle behind the Go button on the Payments page to automatically run the MH batch payment check on a user-selected day of week and hour. Default is off.

- Schema: added autoMhCheckEnabled, autoMhCheckDayOfWeek, autoMhCheckHour to User model
- Backend: new mhBatchPaymentService (shared logic), GET/PUT /auto-mh-check-setting routes, hourly cron job that fires on matching day+hour
- Frontend: toggle + day select (Mon–Sun) + time select (hourly) that persist immediately to DB

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/db/shared/helpers/decimal-helpers.ts

@@ -1,8 +1,7 @@
 import * as z from 'zod';
 
-import type { Prisma } from '../../generated/prisma';
-
-import Decimal from "decimal.js";
+import { Prisma } from '../../generated/prisma';
+import Decimal from 'decimal.js';
 
 // DECIMAL HELPERS
 //------------------------------------------------------
@@ -24,7 +23,7 @@ export const isValidDecimalInput = (
   if (v === undefined || v === null) return false;
   return (
     // Explicit instance checks first
-    v instanceof Decimal ||
+    v instanceof Prisma.Decimal ||
     // If Decimal.js is present and imported by the generator, this symbol exists at runtime
     // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-ignore - Decimal may be undefined when not installed; codegen controls the import