fix(oppo): strip empty params from submit body to fix sign mismatch (errno=800004)

OPPO server includes all received body params in server-side signature computation;
sending empty-string optional params while excluding them from the client-side sign
produces a mismatch. Remove empty entries from params map before building both the
api_sign and the POST body so both sides operate on identical param sets.

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

update-service/src/main/java/com/xuqm/update/service/StoreSubmissionService.java

@@ -2050,6 +2050,9 @@ public class StoreSubmissionService {
         params.put("business_mobile", appInfo.path("business_mobile").asText(""));
         params.put("copyright_url", appInfo.path("copyright_url").asText(appInfo.path("electronic_cert_url").asText("")));
         params.put("electronic_cert_url", appInfo.path("electronic_cert_url").asText(""));
+        // OPPO sign algorithm excludes empty-string params; sending them in the body causes
+        // server-side signature mismatch (errno=800004). Strip empties from both sign and body.
+        params.entrySet().removeIf(e -> e.getValue() == null || e.getValue().isEmpty());
         String requestUrl = oppoRequestUrl("https://oop-openapi-cn.heytapmobi.com/resource/v1/app/upd", params, token, false, clientSecret);
         HttpHeaders headers = new HttpHeaders();
         headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);