PlanetFocus Build 193 - Delta-V reference map cache/local override folder

PlanetFocus first looks for an original local file, then uses its verified
remote source as a fallback and caches the bytes here.

Recognized local filenames:
- stock_community_dark.jpg
- OPM_DeltaV.png
- Kcalbeloh dv Map - Dark.png
- JNSQ_DeltaV_Dark.png
- QuackPackDVMapDark.png

For NoDerivatives maps (Kcalbeloh, JNSQ, QuackPack), place ONLY the original
unaltered file here. PlanetFocus zoom/pan is performed at runtime and does not
rewrite the asset.

Build194 viewer notes
---------------------
PlanetFocus now remembers zoom/pan per map, offers AJUSTER/LECTURE framing,
can switch OPM/QuackPack manually when both are installed, and can display both
official Kcalbeloh Bright/Dark originals. Existing local files are always tried
before network retrieval.
