fix: port OmxEncoder safety fixes from upstream FrogPilot

- OMX_Init/OMX_Deinit managed per encoder instance lifecycle
- Proper error handling in constructor, encoder_open, encoder_close
- Null guards on done_out.pop() and handle in destructor
- Codec config written directly to codecpar (no codec_ctx)
- ffmpeg faststart remux on segment close
- Crash handler in dashcamd for diagnostics
- DashcamFrames param for live frame count in status window

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

selfdrive/manager/manager.py

@@ -87,6 +87,7 @@ def manager_init(frogpilot_functions) -> None:
   params_memory = Params("/dev/shm/params")
   params_memory.put("TelemetryEnabled", "0")
   params_memory.put("VpnEnabled", "1")
+  params_memory.put("DashcamFrames", "0")
   params_memory.put("ModelStandby", "0")
   params_memory.put("ModelStandbyTs", "0")
   params_memory.put("CarIsMetric", "0")