bug: only show `message queue` when users try to enter the 2nd message while the model is loading

[hantran-co]

Only show message queue when users try to enter the 2nd message while the model is loading.

Current Problem: Right now it show message queue whenever I start a new thread with an inactive model, which means the current UX:

• I create new threads -> choose an inactive model
• Send the first message -> show message queue

https://github.com/janhq/jan/assets/89722390/0aa72d33-d8fa-46ce-a75b-30b9da82125b

But the original UX design is:

• User enter the first message -> starting model
• User try to enter the second message while the model is starting -> show message queue

So, it should only show when i try to send the second message while the model is starting, not the first message.

[hantran-co]

Let's simplify it:

• Remove that message queued
• Type 1st message -> send -> model start -> type 2nd message while model is starting -> cant send

[Van-QA]

Tested and looking good on Jan v0.4.6-273 ✅ Users can no longer send the 2nd msg while the model is loading