Add mode-aware expose templates and dynamic camera telemetry

- Add snapshot_imaging.py (cam, scicam1.fits) and snapshot_spectro.py
  (cam2, scicam2.fits) as mode-specific sequencer templates; fix all
  cam2. → cam. bugs in snapshot_spectro
- Update viewer.ini station1/scicam path: scicam.fits → scicam1.fits
- Add template key to MODE_CONFIG in control.js; expose button now
  sends snapshot_imaging or snapshot_spectro depending on active mode
- Add data-status-suffix to camera-dependent telemetry elements so
  applyMode() can switch them between camera-* and camera2-* live

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