feat(1099): show payer EIN on church profile page and 1099-NEC PDF

Populate the PAYER's TIN (EIN) box in Form1099FormService.BuildCopyBHtml
from ChurchProfile.PayerEin (blank when null, matching prior behaviour).
Add payerEin field to ChurchProfileDto TS model (flows into
UpdateChurchProfileRequest via the existing Omit type) and a text input on
the Church Info tab of the church-profile settings page, mirroring the
Routing # field pattern. CSV left unchanged — adding a payer context line
would break the existing ExportFilingCsvAsync assertion (3 lines expected).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

API/ROLAC.API/Services/Form1099/Form1099FormService.cs

@@ -94,7 +94,7 @@ public class Form1099FormService : I1099FormService
         var recipientAddress = JoinAddress(
             JoinLines(payee.AddressLine1, payee.AddressLine2), payee.City, payee.State, payee.Zip);
 
-        // ChurchProfile has no payer EIN/TIN field, so the payer-TIN box is labelled but left blank.
+        var payerEin  = string.IsNullOrWhiteSpace(church.PayerEin) ? "" : church.PayerEin;
         var maskedTin = string.IsNullOrWhiteSpace(payee.TinLast4) ? "" : $"***-**-{payee.TinLast4}";
 
         return
@@ -109,7 +109,7 @@ public class Form1099FormService : I1099FormService
             $"{Encode(church.Name)}<br/>{payerAddress}" +
             "</td>" +
             "<td width=\"50%\" valign=\"top\">" +
-            "<b>PAYER&rsquo;s TIN (EIN)</b><br/>&nbsp;" +
+            $"<b>PAYER&rsquo;s TIN (EIN)</b><br/>{Encode(payerEin)}" +
             "</td></tr>" +
 
             "<tr><td valign=\"top\">" +