Problem\nRunning tmux-mobile emits verbose internal server/runtime logs (websocket lifecycle and tmux attach details) to stdout/stderr by default.\n\n## Expected\nInternal runtime debug logs should not print to stdout/stderr by default.\n\n## Acceptance Criteria\n- By default, internal logger output is silent.\n- Providing --debug-log or TMUX_MOBILE_DEBUG_LOG writes internal logs to the file.\n- Existing user-facing startup output (URLs/QR/password) remains unchanged.\n