feat: install shadcn/ui component primitives

Adds 24 shadcn/ui component files to src/components/ui/ via the shadcn CLI, installs required @radix-ui/* and related dependencies, and updates components.json aliases to resolve under src/.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components.json

@@ -11,10 +11,10 @@
     "prefix": ""
   },
   "aliases": {
-    "components": "@/components",
-    "utils": "@/lib/utils",
-    "ui": "@/components/ui",
-    "lib": "@/lib",
-    "hooks": "@/hooks"
+    "components": "@/src/components",
+    "utils": "@/src/lib/utils",
+    "ui": "@/src/components/ui",
+    "lib": "@/src/lib",
+    "hooks": "@/src/hooks"
   }
 }