refactor: extract pointing math and telemetry into separate modules

Split integrator.py into three focused modules:
- pointing.py: coordinate math (IMU dead-reckoning, plate-solve
  integration, roll/constellation/altaz finalization)
- telemetry.py: TelemetryManager facade (recording, replay,
  command dispatch, image saving, replay event handling)
- integrator.py: main loop and queue plumbing only

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mrosseel