fix(tasks): skip duplicate check when reprocessing and enable retry from failed pipeline step

- Add file_id parameter to process_document to skip duplicate hash check on reprocess
- Pass file_id from reprocess_single_file and bulk_reprocess_files endpoints
- Extend retry-subtask endpoint to support pipeline steps (process_document,
  process_with_azure_document_intelligence, extract_metadata_with_gpt,
  embed_metadata_into_pdf) in addition to upload tasks
- Add retry button for failed main pipeline steps in file detail UI
- Add comprehensive tests for reprocessing and pipeline step retry

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/templates/file_detail.html

@@ -799,6 +799,15 @@
           {% if stage.status == 'not_run' %}
           <div style="color: #718096; font-size: 0.875rem; font-style: italic;">Not executed</div>
           {% endif %}
+          {% if stage.can_retry and stage.status == 'failure' %}
+          <button 
+            id="retry-btn-{{ stage.key }}" 
+            class="retry-btn" 
+            onclick="retrySubtask('{{ stage.key }}', 'retry-btn-{{ stage.key }}')"
+            style="margin-top: 0.5rem;">
+            <i class="fas fa-redo"></i> Retry from this step
+          </button>
+          {% endif %}
           {% if stage.timestamp %}
           <div class="flow-timestamp">
             {{ stage.timestamp.strftime('%Y-%m-%d %H:%M:%S') }}