feat(admin): normalize Persian/Arabic digits in every numeric field

Users typing on a Persian keyboard produced two distinct failures. Fields with
type="number" silently returned an empty string — the browser rejects Persian
digits, so the value was lost and saved as empty or zero. Text fields passed the
Persian characters straight through to the database, where a mobile stored as
۰۹۱۲… never matches 09… again. The secretary form hit the second case with no
validation at all.

Frontend:
- Adds digitsOnly() and the national-code schemas to lib/utils, plus lib/forms
  with numericField()/latinDigitsField() wrappers for React Hook Form fields.
- Converts every type="number" input to type="text" inputMode="numeric" with
  digit normalization; none remain. Fields that legitimately carry non-digits
  (sheba, landline) only get the digits translated, keeping IR and separators.
- Points the patient national-code and mobile schemas at the shared normalizing
  schemas, which accept Persian input instead of rejecting it.
- Drops two duplicate local digit converters in favour of the shared helper.

Backend:
- Adds NumericFieldNormalizerSubscriber, translating digits in whitelisted
  numeric keys of JSON request bodies under /api/v1/ before controllers run, so
  nobat724_front and clinic-pro-tauri are covered too. Translation only — no
  characters are stripped, non-string values and other keys are untouched.

Three component tests asserted on role="spinbutton" and numeric input values;
both are properties of type="number", so they were updated to match the new
text inputs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

assets/admin/components/inventory/AddItemModal.tsx

@@ -1,7 +1,7 @@
 import React, { useEffect, useState } from 'react';
 import Modal from '../ui/Modal';
 import SearchableSelect from '../ui/SearchableSelect';
-import { rialToToman, tomanToRial, toEnglishDigits } from '../../lib/utils';
+import { rialToToman, tomanToRial, digitsOnly } from '../../lib/utils';
 import type { InventoryItem, InventoryMeta, ItemPayload } from '../../hooks/useInventory';
 
 interface Props {
@@ -26,7 +26,6 @@ interface FormState {
 const DEFAULT_UNIT = 'عدد';
 const BLANK: FormState = { name: '', consumable: '', category: '', unit: DEFAULT_UNIT, price: '', stock: '', alertThreshold: '' };
 
-const digits = (v: string) => toEnglishDigits(v).replace(/\D/g, '');
 // group thousands: "1200000" → "1,200,000"
 const group = (v: string) => v.replace(/\B(?=(\d{3})+(?!\d))/g, ',');
 
@@ -54,7 +53,7 @@ export default function AddItemModal({ open, editing, meta, saving, onClose, onS
   const set = (k: keyof FormState) => (e: React.ChangeEvent<HTMLInputElement>) =>
     setForm((f) => ({ ...f, [k]: e.target.value }));
   const setNum = (k: keyof FormState) => (e: React.ChangeEvent<HTMLInputElement>) =>
-    setForm((f) => ({ ...f, [k]: digits(e.target.value) }));
+    setForm((f) => ({ ...f, [k]: digitsOnly(e.target.value) }));
   const setSelect = (k: keyof FormState) => (v: string | number | null) =>
     setForm((f) => ({ ...f, [k]: v == null ? '' : String(v) }));