Print "remaps" upon Proxy start

[teremterem]

It would be nice to see what "remaps" are actually in effect when we start the proxy:

REMAP_CLAUDE_HAIKU_TO=gpt-5-mini-reason-minimal
REMAP_CLAUDE_SONNET_TO=gpt-5-reason-medium
REMAP_CLAUDE_OPUS_TO=gpt-5-reason-high

A user may forget what was previously set in .env, because it was edited ages ago, or for other reasons, so printing the remaps in effect upon Proxy start would be nice.

[teremterem]

Maybe even all the configuration... (or, at least, those settings that differ from their defaults ?)