fix: +redirects with a Base URL

[nitedani]

Opus 5.5 (high effort) wrote this and the code; another Opus 5.5 (high effort) reviewed it. WIP

With a Base URL, a +redirects entry answers 500 instead of 301 whenever the server passes Vike the full request URL, as Vike's built-in server, vike(app) and a +server.js do.

+redirects: { '/old-portal': '/portal' }, BASE=/app/	main	This PR
GET /app/old-portal, +server: true, vike dev	500, [vike@0.4.267][Bug] … at prependBase … at getPermanentRedirect	301, location: http://localhost:3000/app/portal
The same after vike build, node dist/server/index.mjs	500, the same [Bug]	301, the same location

getPermanentRedirect() passed the whole target URL, origin included, to prependBase(), which expects a path. It now prepends the Base URL to the pathname only, with modifyUrlPathname(), which the function already uses a few lines above. A server that passes a path (vike dev and vike preview without +server) gets the same Location as before.

What you should see

1. A new run of test/plusMiddlewares' Base URL tests with +server: true in vike dev (.test-base-dev-server) fails on main and passes here:

# main (test commit only)
AssertionError: expected 500 to equal 301   (.testRun-base.ts:16)
# this PR
PASS

It's the only test of a Base URL where Vike gets the full request URL, as it does behind its built-in server, vike(app) and a +server.js.

As brillout asked, 0ab0638 removes that test before merge; the fix itself is unchanged.

2. Production, with the query string kept:

GET /app/old-portal      -> 301 location: http://localhost:3000/app/portal
GET /app/old-portal?a=1  -> 301 location: http://localhost:3000/app/portal?a=1
GET /app/portal          -> 200

🤖 Generated with Claude Code

[brillout]

Remove the test then squash-merge (use the PR title as the entire commit message).