fix(i18n): translate timeline sr-only labels in en/es locales

timeline_layer_* and timeline_derived_* shipped German values in the
English and Spanish catalogs, so EN/ES screen-reader users heard German
for the world/family layer and birth/death/marriage cues. Translate them;
de.json stays canonical.

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

frontend/messages/en.json

@@ -1041,11 +1041,11 @@
 	"timeline_letters_count": "{count} letters",
 	"timeline_strip_expand": "Show letters",
 	"timeline_range_aria": "Period: {from} to {to}",
-	"timeline_layer_world": "Weltgeschehen",
-	"timeline_layer_family": "Familie",
-	"timeline_derived_birth": "Geburt",
-	"timeline_derived_death": "Tod",
-	"timeline_derived_marriage": "Heirat",
+	"timeline_layer_world": "World events",
+	"timeline_layer_family": "Family",
+	"timeline_derived_birth": "Birth",
+	"timeline_derived_death": "Death",
+	"timeline_derived_marriage": "Marriage",
 	"error_geschichte_not_found": "The story was not found.",
 	"error_journey_item_not_found": "The journey item was not found.",
 	"error_journey_item_position_conflict": "The order was just changed by someone else — please reload the page.",

frontend/messages/es.json

@@ -1041,11 +1041,11 @@
 	"timeline_letters_count": "{count} cartas",
 	"timeline_strip_expand": "Mostrar cartas",
 	"timeline_range_aria": "Período: {from} a {to}",
-	"timeline_layer_world": "Weltgeschehen",
-	"timeline_layer_family": "Familie",
-	"timeline_derived_birth": "Geburt",
-	"timeline_derived_death": "Tod",
-	"timeline_derived_marriage": "Heirat",
+	"timeline_layer_world": "Acontecimientos mundiales",
+	"timeline_layer_family": "Familia",
+	"timeline_derived_birth": "Nacimiento",
+	"timeline_derived_death": "Fallecimiento",
+	"timeline_derived_marriage": "Matrimonio",
 	"error_geschichte_not_found": "No se encontró la historia.",
 	"error_journey_item_not_found": "No se encontró el elemento del viaje.",
 	"error_journey_item_position_conflict": "El orden fue cambiado por otra persona — por favor recargue la página.",

frontend/src/lib/timeline/eventCardConfig.ts

@@ -9,7 +9,7 @@ export type TimelineAccent = 'derived' | 'curated' | 'historical';
 export interface AccentConfig {
 	/** Visible Unicode glyph — render `aria-hidden`, paired with an sr-only label. */
 	glyph: string;
-	/** German layer/life-event label — used as the sr-only text and as visible chrome. */
+	/** Localized layer/life-event label — used as the sr-only / aria text only. */
 	label: string;
 	accent: TimelineAccent;
 }