feat(ocr): move training cards from system page to OCR overview page

OcrTrainingCard and SegmentationTrainingCard now live on the dedicated
OCR overview page. System page no longer fetches training info.
SegmentationTrainingCard updated to use shared TrainingRun type.

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

frontend/src/routes/admin/system/page.svelte.spec.ts

@@ -78,8 +78,6 @@ describe('Admin system page — mass import card', () => {
 					startedAt: null
 				})
 			})
-			// training info fetch → empty
-			.mockResolvedValueOnce({ ok: true, json: async () => ({}) })
 			// trigger POST → returns RUNNING immediately
 			.mockResolvedValueOnce({
 				ok: true,