fix(admin): i18n all hardcoded OCR strings, fix personName lookup, add empty state

- Replace hardcoded EN strings in OcrHealthBar/OcrStatCards/OcrModelsTable with
  Paraglide message keys (de/en/es translations added)
- Add role=img + aria-label to OcrHealthBar status dot
- Add {:else} empty-state row in OcrModelsTable
- Fix personName derivation in [personId]/+page.svelte to use params.personId key
  instead of Object.values()[0] (fragile when multiple persons present)
- Update OcrModelsTable spec to assert empty-state row structure (locale-agnostic)
- Add missing availableSegBlocks test to OcrStatCards spec

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

frontend/messages/es.json

@@ -300,6 +300,22 @@
 	"history_field_tags": "Etiquetas",
 	"admin_tab_system": "Sistema",
 	"admin_tab_ocr": "OCR",
+	"ocr_status_online": "En línea",
+	"ocr_status_offline": "Sin conexión",
+	"ocr_stat_training_blocks": "Bloques de entrenamiento",
+	"ocr_stat_total_blocks": "Total de bloques",
+	"ocr_stat_documents": "Documentos",
+	"ocr_stat_seg_blocks": "Bloques de seg.",
+	"ocr_table_person": "Persona",
+	"ocr_table_cer": "TCE",
+	"ocr_table_accuracy": "Precisión",
+	"ocr_table_lines": "Líneas",
+	"ocr_table_actions": "Acciones",
+	"ocr_table_details": "Detalles",
+	"ocr_no_models": "Aún no hay modelos de remitente entrenados.",
+	"ocr_sender_models_heading": "Modelos de remitente",
+	"ocr_global_history_link": "Historial global →",
+	"ocr_global_history_heading": "Historial global",
 	"admin_system_backfill_heading": "Completar datos de historial",
 	"admin_system_backfill_description": "Crea una entrada de historial inicial para todos los documentos que aún no tienen ninguna (p.ej. documentos importados). Así, en la próxima edición solo se resaltarán los campos realmente modificados.",
 	"admin_system_backfill_btn": "Completar ahora",