Remove Next.js/React legacy files

The project migrated to Angular 18; Next.js artifacts were still present.

Deleted:
- next.config.js, next-env.d.ts (.next/ was already gitignored)
- public/ (favicons/fonts/images duplicated in src/assets/; not served by Angular)
- .env.development, .env.production, .env.sample (Angular uses src/environments/)
- src/middleware.ts (Next.js middleware)
- src/modules/ (React TSX components — article, auth, profile)
- src/utils/ (Next.js api client, iron-session auth, types)
- src/config/ (process.env-based constants)
- src/generated/ (openapi-typescript generated types)
- src/jumps_02.json (only referenced as a commented-out import)
- docs/ (empty directories)

Updated .gitignore to block .env.* and next.config.js from being re-added.

.gitignore

@@ -54,5 +54,11 @@ sonar.properties
 **/*.copy.scss
 **/*.copy.html
 
+# Next.js (legacy, removed)
 .next/
-next-env.d.ts
+next-env.d.ts
+next.config.js
+
+# Environment files (Angular uses src/environments/*.ts)
+.env
+.env.*