feat(02-01): gate the public presentation path

- 404 /_presentations before the SPA shell
- serve /prezentacje/{slugHash} only when presentations is active
- rebuild the embedded student app

static.go

@@ -39,7 +39,7 @@ const defaultAdminPath = "/bmadmin"
 // reservedPrefixes are the path prefixes the student app never answers: the
 // APIs of the plugins and the public uploads. The admin path is added from
 // the configuration.
-var reservedPrefixes = []string{"/_user", "/_bm", "/_quizzes", "/api", "/storage"}
+var reservedPrefixes = []string{"/_user", "/_bm", "/_quizzes", "/_presentations", "/api", "/storage"}
 
 // errMissingIndex reports a tree without index.html (an unbuilt tree).
 var errMissingIndex = errors.New("jz.bm: public/index.html missing; run the frontend build (cd frontend && npm ci && npm run build)")