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/en.json

@@ -300,6 +300,22 @@
 	"history_field_tags": "Tags",
 	"admin_tab_system": "System",
 	"admin_tab_ocr": "OCR",
+	"ocr_status_online": "Online",
+	"ocr_status_offline": "Offline",
+	"ocr_stat_training_blocks": "Training blocks",
+	"ocr_stat_total_blocks": "Total blocks",
+	"ocr_stat_documents": "Documents",
+	"ocr_stat_seg_blocks": "Seg. blocks",
+	"ocr_table_person": "Person",
+	"ocr_table_cer": "CER",
+	"ocr_table_accuracy": "Accuracy",
+	"ocr_table_lines": "Lines",
+	"ocr_table_actions": "Actions",
+	"ocr_table_details": "Details",
+	"ocr_no_models": "No sender models trained yet.",
+	"ocr_sender_models_heading": "Sender Models",
+	"ocr_global_history_link": "Global history →",
+	"ocr_global_history_heading": "Global History",
 	"admin_system_backfill_heading": "Backfill history data",
 	"admin_system_backfill_description": "Creates an initial history entry for all documents that do not have one yet (e.g. imported documents). This ensures that future edits only highlight actually changed fields.",
 	"admin_system_backfill_btn": "Backfill now",