fix(scholars): improve validation, fix delete, add status badges

- Extract scholar ID parsing to dedicated module with robust URL
  handling (trailing slashes, fragments, extra query params, encoded
  characters) and per-token error feedback showing why each invalid
  entry was skipped
- Wrap delete_scholar DB commit in IntegrityError handler so cascade
  failures return a proper API error instead of 500
- Add ScholarStatusBadges component showing Pending/Failed/Partial/OK
  badges on scholar rows based on baseline_completed and last_run_status
- Show Pending badge in ScholarSettingsModal for unscraped scholars
- Surface failed_count and partial_count in dashboard latest run summary
  and recent run list items
- Extend backend validator tests with edge cases (empty, whitespace,
  unicode, URL-as-ID)
- Add integration tests for DELETE 404, DELETE with cascade, and POST
  with corrupted scholar_id
- Add comprehensive frontend tests for parsing logic and component
  behavior

app/api/routers/scholars.py

@@ -261,11 +261,18 @@ async def delete_scholar(
             code="scholar_not_found",
             message="Scholar not found.",
         )
-    await scholar_service.delete_scholar(
-        db_session,
-        profile=profile,
-        upload_dir=settings.scholar_image_upload_dir,
-    )
+    try:
+        await scholar_service.delete_scholar(
+            db_session,
+            profile=profile,
+            upload_dir=settings.scholar_image_upload_dir,
+        )
+    except scholar_service.ScholarServiceError as exc:
+        raise ApiException(
+            status_code=409,
+            code="scholar_delete_failed",
+            message=str(exc),
+        ) from exc
     structured_log(
         logger, "info", "api.scholars.deleted", user_id=current_user.id, scholar_profile_id=scholar_profile_id
     )