Support localization for annotation labels and text

Replaced hardcoded annotation labels and text with localized values, falling back to English defaults if not available. Date formatting now adapts to the current locale using getCurrentCulture().

EnvelopeGenerator.Web/wwwroot/js/annotation.js

@@ -112,7 +112,7 @@ async function createAnnotations(document, envelopeId, receiverId) {
         const formFieldDateLabel = new PSPDFKit.FormFields.TextFormField({
             name: id_date_label,
             annotationIds: PSPDFKit.Immutable.List([annotation_date_label.id]),
-            value: "Date",
+            value: localized.date ?? "Date",
             readOnly: true
         })
         //#endregion
@@ -134,7 +134,7 @@ async function createAnnotations(document, envelopeId, receiverId) {
         const formFieldCityLabel = new PSPDFKit.FormFields.TextFormField({
             name: id_city_label,
             annotationIds: PSPDFKit.Immutable.List([annotation_city_label.id]),
-            value: "Ort",
+            value: localized.city ?? "City",
             readOnly: true,
             color: PSPDFKit.Color.BLACK
         })
@@ -157,7 +157,7 @@ async function createAnnotations(document, envelopeId, receiverId) {
         const formFieldPositionLabel = new PSPDFKit.FormFields.TextFormField({
             name: id_position_label,
             annotationIds: PSPDFKit.Immutable.List([annotation_position_label.id]),
-            value: "Position",
+            value: localized.position ?? "Position",
             readOnly: true
         })
         //#endregion
@@ -251,7 +251,7 @@ async function createAnnotationFrameBlob(receiverName, receiverSignature, timest
     ctx.textRendering = "geometricPrecision"
 
     const date = timestamp
-    const dateString = date.toLocaleString('de-DE')
+    const dateString = date.toLocaleString(getCurrentCulture())
 
     const signatureLength = 100 * scale
     const signatureString = receiverSignature.substring(0, 15) + "…"
@@ -275,7 +275,7 @@ async function createAnnotationFrameBlob(receiverName, receiverSignature, timest
 
     ctx.fillStyle = 'black'
     ctx.font = `${fontSize * scale}px sans-serif`
-    ctx.fillText('Signed by', 15 * scale, 10 * scale)
+    ctx.fillText(localized.signedBy ?? 'Signed by', 15 * scale, 10 * scale)
     ctx.fillText(receiverName, 15 * scale, 60 * scale)
     ctx.fillText(signatureString, 15 * scale, 70 * scale)