- Defensive grid-to-coordinate resolution in create_qso (case instead of crash on match failure)
- Log warning when Oban weather enqueue fails instead of silently dropping
- Add 30s per-session submission cooldown to prevent rapid-fire submissions
Maidenhead grid module converts grid squares to lat/lon coordinates.
Submission form validates grids, bands, modes, and email, computes
positions and distance, then triggers the weather/HRRR/terrain
processing pipeline via Oban.
