fix(clients): minor-age threshold to 18, senior/PWD doc reload, in-app document preview dialog

- Raise isMinor threshold from age <10 to <18 (legal definition), cascading correctly to
  guardian requirement, KYC document filtering, and Education Level/Degree Qualification
  visibility (now shown for all ages, not hidden for minors).
- Load and display previously-uploaded Senior Citizen proof / PWD certificate documents on
  edit (view/replace/remove), instead of always showing an empty upload prompt.
- Fix seniorPwdDocsComplete to accept an existing certificate, not just a freshly-picked file.
- Add DocumentPreviewDialogComponent: a reusable in-app modal (image/PDF/download) used in
  place of window.open() for saved KYC/address/senior-citizen/PWD documents — avoids popup
  blockers (fired only after the async download resolved) and Chrome/Edge's failure to paint
  large base64 data: URLs on first open.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/clients/client-stepper/client-kyc-step/client-kyc-step.component.ts

@@ -32,6 +32,7 @@ import { ProofType, normalizeProofType, groupProofsByCategory } from '../../shar
 import { KycUploadHelperService } from '../../shared/kyc-upload-helper.service';
 import { CaptureImageDialogComponent } from '../../clients-view/custom-dialogs/capture-image-dialog/capture-image-dialog.component';
 import { dataUrlToFile } from 'app/shared/utils/data-url.util';
+import { DocumentPreviewDialogComponent } from '../../shared/document-preview-dialog/document-preview-dialog.component';
 
 @Component({
   selector: 'mifosx-client-kyc-step',
@@ -695,30 +696,17 @@ export class ClientKycStepComponent implements OnInit, OnChanges, OnDestroy {
     this.kycDocMergedPreview = null;
   }
 
-  /**
-   * Open the saved KYC ID-proof document in a new browser tab.
-   *
-   * Same flow as the address-step variant: images use the already-loaded
-   * base64 data URL; PDFs (or anything without a cached preview) are fetched
-   * fresh and rendered via a temporary blob URL.
-   */
+  /** Open the saved KYC ID-proof document in an in-app preview dialog. */
   viewExistingKycDoc(): void {
     if (!this.existingKycIdentifierId || this.existingKycDocuments.length === 0) {
       return;
     }
     const doc = this.existingKycDocuments[0];
-    if (doc.previewUrl) {
-      window.open(doc.previewUrl, '_blank', 'noopener');
-      return;
-    }
     this.clientsService.downloadClientIdentificationDocument(this.existingKycIdentifierId, doc.id).subscribe({
-      next: (blob: Blob) => {
-        const url = URL.createObjectURL(blob);
-        const w = window.open(url, '_blank', 'noopener');
-        if (w) {
-          setTimeout(() => URL.revokeObjectURL(url), 60_000);
-        }
-      },
+      next: (blob: Blob) =>
+        this.dialog.open(DocumentPreviewDialogComponent, {
+          data: { blob, title: doc.fileName || doc.name, fileName: doc.fileName || doc.name }
+        }),
       error: () => {
         /* silent — UI still shows the saved filename */
       }