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

frontend/src/pages/DashboardPage.vue

@@ -494,6 +494,11 @@ watch(
                       <template v-else>
                         Processed {{ displayedLatestRun.scholar_count }} scholars and discovered
                         {{ displayedLatestRun.new_publication_count }} new publications.
+                        <template v-if="displayedLatestRun.failed_count > 0 || displayedLatestRun.partial_count > 0">
+                          <span class="text-state-warning-text">
+                            {{ displayedLatestRun.failed_count > 0 ? `${displayedLatestRun.failed_count} failed` : "" }}{{ displayedLatestRun.failed_count > 0 && displayedLatestRun.partial_count > 0 ? ", " : "" }}{{ displayedLatestRun.partial_count > 0 ? `${displayedLatestRun.partial_count} partial` : "" }}.
+                          </span>
+                        </template>
                       </template>
                     </p>
                   </div>
@@ -527,6 +532,9 @@ watch(
                         </div>
                         <span class="text-xs text-secondary">
                           {{ formatDate(run.start_dt) }} • {{ run.new_publication_count }} new
+                          <template v-if="run.failed_count > 0">
+                            • <span class="text-state-warning-text">{{ run.failed_count }} failed</span>
+                          </template>
                         </span>
                       </li>
                     </ul>