fix dynamic param extraction in edge-ssr-app (#83081)
Fixes edge runtime pages with dynamic routes returning 500 errors when
the URL segment literally contains bracket syntax that matches the
folder name (e.g., accessing `/[id]` for a route defined as
`/[id]/page.tsx`).
The removal of web-server.ts in #81389 modified how route params were
extracted for dynamic routes. The route matcher in prepare() was being
created with the full internal page path (e.g., /[id]/page) which
generated a regex expecting /page at the end. However, actual URL
pathnames don't include the /page suffix, causing the matcher to fail
when trying to extract params. This issue specifically manifested when
the URL contained literal brackets (like /[id]), as the fallback param
extraction would fail and leave params empty, leading to the error.
This PR normalizes the page path using before creating the route matcher
in prepare(). This ensures the regex pattern matches the actual URL
pathname format (without /page suffix).
Fixes NEXT-4698
