Fix: use_backend routing rules not displayed in Bulk Import UI

CRITICAL BUG - use_backend Rules Missing from UI:

Issue:
- Parser extracts use_backend rules
- Backend response includes them (after e3a6470 fix)
- But UI doesn't display them in parse preview
- User can't see routing rules before importing

Root Cause (BulkConfigImport.js Line 703-709):
  UI displays:
    ACL Rules ✓
    Request Headers ✓
    Response Headers ✓
    TCP Rules ✓
    use_backend Rules ✗ (MISSING!)

Fix Applied:
  Added use_backend_rules display section (Line 710-718)
  Shows: Backend Routing Rules (X)
  Format: Same as ACL rules (Text code display)

UI Preview Now Shows:
  ACL Rules (8):
    acl Elasticsearch hdr(host) -i elastic.com
    acl Kibana hdr(host) -i kibana.com

  Backend Routing Rules (8):
    use_backend Elasticsearch if Elasticsearch
    use_backend Kibana if Kibana

Complete Fix Summary (3 parts):
  1. e3a6470: Bulk-create INSERT query
  2. e3a6470: Parse-bulk response data
  3. THIS: Frontend UI display

All three parts now fixed - use_backend rules work end-to-end

backend/routers/config.py

@@ -758,7 +758,8 @@ async def parse_bulk_config(
                 "request_headers": frontend.request_headers,
                 "response_headers": frontend.response_headers,
                 "tcp_request_rules": frontend.tcp_request_rules,
-                "acl_rules": frontend.acl_rules
+                "acl_rules": frontend.acl_rules,
+                "use_backend_rules": frontend.use_backend_rules  # CRITICAL FIX: Include routing rules
             })
         
         backends_data = []

frontend/src/components/BulkConfigImport.js

@@ -709,6 +709,15 @@ backend web-backend
                                       ))}
                                     </Descriptions.Item>
                                   )}
+                                  {frontend.use_backend_rules && frontend.use_backend_rules.length > 0 && (
+                                    <Descriptions.Item label={`Backend Routing Rules (${frontend.use_backend_rules.length})`}>
+                                      {frontend.use_backend_rules.map((rule, idx) => (
+                                        <div key={idx}>
+                                          <Text code style={{ fontSize: '11px' }}>{rule}</Text>
+                                        </div>
+                                      ))}
+                                    </Descriptions.Item>
+                                  )}
                                 </Descriptions>
                               </div>
                             );