fix: use relative URLs for Lighthouse CI static server

The static server serves from dist/ directly, so URLs should not
include the base path prefix.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: braboj

lighthouserc.json

@@ -3,10 +3,10 @@
     "collect": {
       "staticDistDir": "./astro-site/dist",
       "url": [
-        "/tutorial-git/",
-        "/tutorial-git/introduction/",
-        "/tutorial-git/building-blocks/",
-        "/tutorial-git/branching-and-merging/"
+        "/",
+        "/introduction/",
+        "/building-blocks/",
+        "/branching-and-merging/"
       ]
     },
     "assert": {