fix: resolve ruff lint errors and add lint CI job

Remove unused imports (deque, sys, Opcode, struct, _REPLAY_ADJUSTABLE_OPCODES)
across 4 active Python files and refactor semicolons to separate statements
in radar_protocol.py. Add ruff lint job to CI workflow targeting only the
active files (excludes legacy GUI_V*.py and v7/).

9_Firmware/9_3_GUI/test_radar_dashboard.py

@@ -21,7 +21,7 @@ from radar_protocol import (
     HEADER_BYTE, FOOTER_BYTE, STATUS_HEADER_BYTE,
     NUM_RANGE_BINS, NUM_DOPPLER_BINS, NUM_CELLS,
     DATA_PACKET_SIZE,
-    _HARDWARE_ONLY_OPCODES, _REPLAY_ADJUSTABLE_OPCODES,
+    _HARDWARE_ONLY_OPCODES,
 )