fix(transcribe): localise Delete key cap + annotation label, clarify Esc row (#327)

Review follow-up (Leonie, Requirements Engineer): the Delete key cap was a
hardcoded German "Entf" shown to EN/ES users — now driven by key_cap_delete
(Entf/Del/Supr). The annotation read-only aria-label was a hardcoded German
"Block anzeigen" in all locales — now annotation_view_label. Renamed the Esc
row label from "Bereich schließen" to "Panel schließen" so it no longer
collides with "Bereich" (= region) used elsewhere in the cheatsheet.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/messages/es.json

@@ -938,9 +938,11 @@
 	"shortcut_close_panel": "Cerrar panel",
 	"shortcut_help": "Mostrar atajos de teclado",
 	"shortcut_draw_hint": "Arrastre una región con el ratón.",
+	"key_cap_delete": "Supr",
 	"cheatsheet_title": "Atajos de teclado",
 	"cheatsheet_close": "Cerrar el resumen de atajos",
 	"cheatsheet_autosave_hint": "Los cambios se guardan automáticamente.",
+	"annotation_view_label": "Ver bloque",
 	"annotation_label_with_delete": "Mostrar bloque, pulse Supr para eliminar.",
 	"transcription_mode_help_label": "Modo lectura y edición",
 	"transcription_mode_help_body": "Lectura muestra la transcripción como texto continuo. Edición abre los campos de texto para cada pasaje.",