Backend: Add /prefetch-images endpoint that warms the image cache in
parallel using a thread pool, skipping already-cached images.
Frontend: Trigger prefetch on mode init so images load instantly.
Replace per-request Date.now() cache-bust with a 5-minute rotating
key to allow browser caching aligned with backend max-age.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
New mode providing real-time space weather data from NOAA SWPC, NASA SDO,
and HamQSL APIs. Includes Kp index, solar wind, X-ray flux charts, HF band
conditions, D-RAP absorption maps, aurora forecast, solar imagery, flare
probability, and active solar regions. No SDR hardware required.
Bumps version to 2.20.0. Updates all documentation including README, FEATURES,
USAGE, UI_GUIDE, help modal, and GitHub Pages site.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
