fix(http): drop APIHelper's hand-set brotli encoding; LogoHelper sends the real UA

APIHelper advertised `br` though brotli isn't installed, so a server that
honoured it would send a body requests can't decode. LogoHelper sent a bare
`LEDMatrix-Common/1.0`, the kind of User-Agent ESPN has been rejecting.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/common/api_helper.py

@@ -78,7 +78,6 @@ class APIHelper:
             'User-Agent': USER_AGENT,
             'Accept': 'application/json',
             'Accept-Language': 'en-US,en;q=0.9',
-            'Accept-Encoding': 'gzip, deflate, br',
             'Connection': 'keep-alive'
         })