3x-ui v3.7.0 (decoder-dev)

Fork release based on upstream v3.7.0 with decoder-dev patches:

• XHTTP variant B fields (scStreamDownServerSecs, downFrame)
• Responsive mobile UI
• tgId JSON unmarshal fix
• Install/update scripts point to decoder-dev/3x-ui

Install:
bash <(curl -Ls https://raw.githubusercontent.com/decoder-dev/3x-ui/main/install.sh)