optimize: resize client icons to ≤256px and strip metadata

[Savid]

Resized all client icons to fit within 256x256px while maintaining aspect ratios. Stripped metadata to reduce file sizes.

Size reductions:

• tysm.png: 690 KiB → 62 KiB (91% reduction, 1024x1024 → 256x256)
• lodestar.png: 103 KiB → 63 KiB (39% reduction, 250x334 → 192x256)
• teku.png: 70 KiB → 34 KiB (51% reduction, 400x400 → 256x256)
• geth.png: 78 KiB → 37 KiB (52% reduction, 600x600 → 256x256)
• prysm.png: 56 KiB → 24 KiB (57% reduction, 400x400 → 256x256)
• caplin.png: 53 KiB → 29 KiB (45% reduction, 400x400 → 256x256)
• besu.png: 44 KiB → 28 KiB (36% reduction, 294x296 → 254x256)
• nimbusel.png: 9.4 KiB → 2.7 KiB (72% reduction, 329x329 → 256x256)
• grandine.png: 9.2 KiB → 4.0 KiB (56% reduction, 400x400 → 256x256)
• nimbus.png: 3.9 KiB → 1.5 KiB (63% reduction, 400x400 → 256x256)

Total: 831 KiB → 315 KiB (516 KiB saved, 62% overall reduction)