common : cleanup logs and modernize the progress bar (#21215)

```
$ build/bin/llama-server -hf unsloth/Qwen3.5-0.8B-GGUF
common_download_file_single_online: HEAD failed, status: 404
no remote preset found, skipping
Downloading mmproj-BF16.gguf ——————————————————————————————————————— 100%
Downloading Qwen3.5-0.8B-Q4_K_M.gguf ——————————————————————————————— 100%
...
```

Signed-off-by: Adrien Gallouët <[email protected]>