refresh token if necessary when starting a connection

[rinormaloku]

Implements the usage of refresh tokens when a new connection is started.

How to test:

• You need an MCP server that uses OAuth with access and refresh tokens.
• Set the expiry low for the access token so that you can test it quickly.
• Connect first (this will trigger the full MCP Authorization Flow)
• Wait for the token to expire
• Refresh the page and connect again

Observe: The new connection will use refresh token to get a new access token (The full OAuth flow won't be required).

This partially addresses the issue: #608.

To fully support it we need to udpate this function to make use of the refresh token, but it proved rather difficult:

https://github.com/modelcontextprotocol/inspector/blob/main/client/src/lib/hooks/useConnection.ts#L106-L167

[rinormaloku]

@felixweinberger tagging you for visibility