Lab assignment management UI and student variant view

- progress-service: POST /api/v1/assign (manual variant), GET /api/v1/assignments?labId=
  (enriched assignments), fixed enrich() to return real variant number/title/statement
- gateway: routes for /api/v1/assign and /api/v1/levels (exact paths)
- web: lab detail page shows students grouped with level and variant selects,
  group filter, distribute/redistribute buttons, source badge (auto/manual)
- web: student dashboard renders variant statement via libs/markdown (spoilers,
  code highlight, sanitized)
- academic-service: unquote YAML front-matter values (variant numbers were quoted)
- academic-service: LabLevelDetail.id for level references

services/gateway/src/main/resources/application.yml

@@ -20,7 +20,7 @@ spring:
             - id: progress
               uri: ${LMS_PROGRESS_URI:http://localhost:8083}
               predicates:
-                - Path=/api/v1/assignments/**,/api/v1/levels/**,/api/v1/me/**,/api/v1/distribute/**
+                - Path=/api/v1/assign,/api/v1/assign/**,/api/v1/assignments/**,/api/v1/levels,/api/v1/levels/**,/api/v1/me/**,/api/v1/distribute,/api/v1/distribute/**
 
 management:
   endpoints: