wiki: add Carbon Design System icons (2673) + pictograms (1000)

- 2673 SVG icons from @carbon/icons v11.82.0 (~2.5 MB)
- 1000 SVG pictograms from Carbon Design System (~2.0 MB)
- Updated 00-overview.md with asset structure and category listing

All icons: 32x32, fill: currentColor, optimized SVG
All pictograms: 24x24, fill: currentColor, SVG

assets/icons/carbon/letter-Nn.svg

@@ -0,0 +1 @@
+<svg id="icon" viewBox="0 0 32 32"><title>letter--Nn</title><path d="M25,23H23V15H19v8H17V13h6a2,2,0,0,1,2,2Z"/><polygon points="13 19 9.32 9 7 9 7 23 9 23 9 13 12.68 23 15 23 15 9 13 9 13 19"/></svg>