fix(a11y): add aria-label to PDF viewer in signing screen

Adds aria-label='PDF document to sign' to the PdfEditor component
so screen readers and Playwright tests can locate and scope within
the PDF viewer region in the signing view.

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

src/views/SignPDF/SignPDF.vue

@@ -11,6 +11,7 @@
 			ref="pdfEditor"
 			width="100%"
 			height="100%"
+			:aria-label="t('libresign', 'PDF document to sign')"
 			:files="pdfBlobs"
 			:file-names="fileNames.length > 0 ? fileNames : [pdfFileName]"
 			:read-only="true"