feat(browser-agent): Add file logging, fix Nova Act API key error, update BT workflows

- Add fern-based dual logging (console + file) so logs are accessible on
  Windows release builds where the GUI subsystem has no console attached.
  Log files written to platform-specific logs directory with daily rotation
  and automatic cleanup of files older than 7 days.
- Fix login setup failing with "Failed to get Nova Act API key" when using
  OpenAI models by making the API key optional for commands like
  setup_login that don't require LLM access.
- Update BT broadband template and ready example: switch to DOM-based
  extraction, add WaitForResults retry sequence, remove debug screenshots.
- Bump version to 0.4.26.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: guyernest