fix(geoportal-v2): exclude /api/basemap-style/* from middleware auth gate

MapLibre fetches the style URL from the browser as a `style:` source.
For raster/style fetches it doesn't always carry the session cookie
(varies by browser + request mode + cross-origin policy), so the
middleware was hitting it with 401 "Authentication required" and the
liberty basemap silently failed to load — back to the empty cream
sheet we just fixed yesterday.

The /api/basemap-style/[id] proxy returns a publicly-cached
OpenFreeMap style with no user data — no reason to keep it behind auth.
Adding it to the matcher's bypass list lets the browser fetch it
cookie-less and the basemap renders correctly for everyone.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/middleware.ts

@@ -58,6 +58,6 @@ export const config = {
      * - /favicon.ico, /robots.txt, /sitemap.xml
      * - Files with extensions (images, fonts, etc.)
      */
-    "/((?!api/auth|api/version|api/notifications/digest|api/eterra/auto-refresh|api/compress-pdf|api/address-book|api/projects|auth/signin|_next|favicon\\.ico|robots\\.txt|sitemap\\.xml|.*\\..*).*)",
+    "/((?!api/auth|api/version|api/basemap-style|api/notifications/digest|api/eterra/auto-refresh|api/compress-pdf|api/address-book|api/projects|auth/signin|_next|favicon\\.ico|robots\\.txt|sitemap\\.xml|.*\\..*).*)",
   ],
 };