fix(deploy): use valid HF Space color (yellow, not orange)

HF metadata validator only allows colorFrom in
[red, yellow, green, blue, indigo, purple, pink, gray].
Yellow is closest to the Orange brand color.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -1,7 +1,7 @@
 ---
 title: FiberGate
 emoji: 🏗️
-colorFrom: orange
+colorFrom: yellow
 colorTo: gray
 sdk: docker
 app_port: 8000