fix(job): guard group conversation in MixinJob.createConversation (#6416)

* fix(job): skip auto-create for group conversation in checkConversationExist

The createConversation path in MixinJob builds a minimal ConversationRequest
without random_id, name, announcement, or full participants. When a GROUP
conversation falls into SendMessageJob's checkConversationExist with a
non-SUCCESS status, it triggers /conversations create with category=GROUP
but no random_id, which the server rejects (missing or invalid UUID).

Short-circuit groups here so creation stays on the proper flow via
GroupViewModel / ConversationListViewModel.createGroupConversation, which
always supplies a valid randomId.

* fix(job): guard against group conversation in createConversation

createConversation builds a minimal ConversationRequest without random_id,
name, or full participants, which is only valid for CONTACT (1v1) where
the conversationId is deterministically derived from two userIds. If a
GROUP slips into this path (e.g. SendMessageJob.checkConversationExist on
a non-SUCCESS local group), the /conversations POST hits the server with
category=GROUP but no random_id, yielding 'invalid UUID' or missing-param
errors and a broken group on the server.

Bail out early for groups and report the unexpected state so the proper
GroupViewModel / ConversationListViewModel flow remains the only path
that creates groups.

---------

Co-authored-by: Crossle Song <crosslesong@gmail.com>

Author: SeniorZhai

app/src/main/java/one/mixin/android/job/MixinJob.kt

@@ -182,6 +182,13 @@ abstract class MixinJob(
     }
 
     private fun createConversation(conversation: Conversation): Long? {
+        if (conversation.isGroupConversation()) {
+            reportException(
+                "Skip MixinJob.createConversation for group",
+                IllegalStateException("conversation_id=${conversation.conversationId}"),
+            )
+            return conversation.expireIn
+        }
         val request =
             ConversationRequest(
                 conversationId = conversation.conversationId,