fix: Linux/Wayland support with evdev, toggle-in-PTT, debug mode

[aberglund-cf]

• Replace rdev (X11-only) with evdev for global hotkey on Linux

  • hotkey_linux.rs: reads /dev/input/event* directly, works on Wayland
  • hotkey_macos.rs: rdev-based backend (unchanged behavior on macOS)
  • Detailed error diagnostics for missing input group permissions

• Fix PTT on Linux: suppress KeyUp+Toggle double-fire from evdev

  • suppress_next_toggle flag prevents re-starting recording on key release
  • Terminal keyboard (space) now works as toggle even in PTT mode

• Fix welcome banner shifting (raw mode \n vs \r\n race)

  • Print banner before spawning keyboard thread

• Add 10Hz UI tick timer for recording duration and transcribing spinner

• Add --debug mode: no animated display, plain log lines to stderr

  • Logs key events, device name, audio levels, duration, transcript
  • Skips OpenCode injection and connectivity check
  • --port not required in debug mode
  • Uses \r\n for correct output in raw mode

• Suppress JACK/ALSA startup noise via env vars (JACK_NO_START_SERVER etc)

• Update welcome banner to show both hotkey and terminal toggle inputs