chore: move src/llama_stack/ui to src/llama_stack_ui (#4068)

# What does this PR do?
This better separates UI from backend code, which was a point of
confusion often for our beloved AI friends.


## Test Plan
CI

src/llama_stack/ui/components.json

@@ -1,21 +0,0 @@
-{
-  "$schema": "https://ui.shadcn.com/schema.json",
-  "style": "new-york",
-  "rsc": true,
-  "tsx": true,
-  "tailwind": {
-    "config": "",
-    "css": "app/globals.css",
-    "baseColor": "neutral",
-    "cssVariables": true,
-    "prefix": ""
-  },
-  "aliases": {
-    "components": "@/components",
-    "utils": "@/lib/utils",
-    "chat": "@/components/chat",
-    "lib": "@/lib",
-    "hooks": "@/hooks"
-  },
-  "iconLibrary": "lucide"
-}