fix: restore dark theme tokens for login/admin/legal pages + remove formation SEO

- globals.css: restore missing dark-*, primary, error, warning color tokens
  and gradient-text/gradient-bg utility classes so login, admin, mentions-legales,
  and confidentialite pages render correctly (white text was invisible on white bg)
- layout.tsx: remove "Candidature Formation" from JSON-LD SiteNavigationElement
- candidature/layout.tsx: remove "Formation" from title/description, add noindex
- robots.ts: disallow /candidature/ from crawlers
- sitemap.ts: remove /candidature from sitemap

https://claude.ai/code/session_01V8YAjpqRQ3bfBYsABYsEgo

app/sitemap.ts

@@ -34,14 +34,6 @@ export default function sitemap(): MetadataRoute.Sitemap {
       priority: 0.9,
     },
 
-    // Candidature - page importante
-    {
-      url: `${BASE_URL}/candidature`,
-      lastModified: now,
-      changeFrequency: "monthly",
-      priority: 0.8,
-    },
-
     // Pages SEO locales - site internet artisan + ville
     {
       url: `${BASE_URL}/site-internet-artisan-douai`,