feat: input field saiz font No IC dalam konfigurasi template

- Tambah fields[name][ic_font_size] dalam form — baris: Warna | Saiz Font No IC | Align
- Default: 70% daripada saiz font nama (sebelum ini hardcode 50%)
- loadPreview() hantar ic_font_size terkini ke endpoint pratonton
- writeIcBelow() baca ic_font_size dari config, fallback 70% jika tiada
- Validasi updateConfig: ic_font_size nullable|integer|min:8|max:200

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

app/Http/Controllers/Admin/CertificateTemplateController.php

@@ -55,6 +55,7 @@ class CertificateTemplateController extends Controller
             'fields.*.x'              => 'required|integer|min:0',
             'fields.*.y'              => 'required|integer|min:0',
             'fields.*.font_size'      => 'required|integer|min:8|max:200',
+            'fields.*.ic_font_size'   => 'nullable|integer|min:8|max:200',
             'fields.*.font_color'     => 'required|string|max:20',
             'fields.*.align'          => 'required|in:left,center,right',
         ]);