Three issues causing themes to look nearly identical:
1. blob3 was never rendered — each theme defines 4 blob colors but
MeshBackground only used blob1/blob2/blob4. Added blob3 (honey
for Amber, indigo for Blau, etc.) as a 4th blob.
2. Blob alpha too low — dark 0.22-0.30, light ×0.55 made blobs
almost invisible. Increased to 0.30-0.42 dark, ×0.65 light.
Now Amber clearly shows warm golds/corals, Blau shows cool
sky/cyan/indigo — themes are visually distinct.
3. Vignette too aggressive — 0.55 alpha covered blob edges.
Reduced to 0.40 so theme colors reach further into corners.
4ebe812c42