i18n(transcription): add reader read-label and panel title strings (#697)

transcription_read_label ("Transkription lesen") for the read-only entry
control and transcription_panel_title ("Transkription") for the plain
header readers see instead of the Lesen/Bearbeiten toggle.

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

frontend/messages/de.json

@@ -603,6 +603,8 @@
 	"doc_details_no_tags": "Keine Schlagwörter zugeordnet",
 	"doc_details_more_receivers": "+{count} weitere",
 	"transcription_mode_label": "Transkribieren",
+	"transcription_read_label": "Transkription lesen",
+	"transcription_panel_title": "Transkription",
 	"transcription_mode_stop": "Fertig",
 	"transcription_block_placeholder": "Text eingeben — mit @Name eine Person aus dem Archiv verknüpfen",
 	"transcription_block_save_saving": "Speichere...",

frontend/messages/en.json

@@ -603,6 +603,8 @@
 	"doc_details_no_tags": "No tags assigned",
 	"doc_details_more_receivers": "+{count} more",
 	"transcription_mode_label": "Transcribe",
+	"transcription_read_label": "Read transcription",
+	"transcription_panel_title": "Transcription",
 	"transcription_mode_stop": "Done",
 	"transcription_block_placeholder": "Type text — use @name to link a person from the archive",
 	"transcription_block_save_saving": "Saving...",

frontend/messages/es.json

@@ -603,6 +603,8 @@
 	"doc_details_no_tags": "No hay etiquetas asignadas",
 	"doc_details_more_receivers": "+{count} más",
 	"transcription_mode_label": "Transcribir",
+	"transcription_read_label": "Leer transcripción",
+	"transcription_panel_title": "Transcripción",
 	"transcription_mode_stop": "Listo",
 	"transcription_block_placeholder": "Escriba el texto — use @nombre para vincular a una persona del archivo",
 	"transcription_block_save_saving": "Guardando...",