Add support download model for author:model

[namchuai]

Describe Your Changes

• Refactoring download service to use Result
• Add support download model for author:model
• Update download model, engine Http Apis

Screenshots

CURLs for HTTP API

1. Download cortexso

curl --location 'http://127.0.0.1:3928/models/pull' \
--header 'Content-Type: application/json' \
--data '{
    "modelId": "tinyllama:gguf"
}'

2. Download with direct url

curl --location 'http://127.0.0.1:3928/models/pull' \
--header 'Content-Type: application/json' \
--data '{
    "modelId": "https://huggingface.co/TheBloke/Mistral-7B-Instruct-v0.1-GGUF/blob/main/mistral-7b-instruct-v0.1.Q2_K.gguf"
}'

Fixes Issues

• bug: Model download fails due to YAML::BadFile #1325

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed

[vansangpfiev]

Thanks for refactoring. The codebase looks much better now.