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/src/lib/document/transcription/ShortcutCheatsheet.svelte

@@ -16,7 +16,7 @@ const groups = [
 		{ cap: 'e', label: m.shortcut_toggle_mode() },
 		{ cap: 'n', label: m.shortcut_new_region() },
 		{ cap: 't', label: m.shortcut_toggle_training() },
-		{ cap: 'Entf', label: m.shortcut_delete_region() }
+		{ cap: m.key_cap_delete(), label: m.shortcut_delete_region() }
 	],
 	[
 		{ cap: 'Esc', label: m.shortcut_close_panel() },