fix: obfuscate email in contact links, raise rate limits, make Libre toggleable

- about.php: use EmailObfuscator::email() for contact email link text instead of htmlspecialchars
- SearchController: raise rate limit from 30 to 300 req/min
- request-access.php: raise rate limit from 3 to 30 req/10min
- partage/index.php: raise rate limit from 5 to 50 req/10min
- contenus.php: make Libre option toggleable (remove disabled class), move to top of Degré d'ouverture, remove temporary note about next academic year

app/src/Controllers/SearchController.php

@@ -22,7 +22,7 @@
  */
 class SearchController
 {
-    private const RATE_LIMIT_MAX = 30;
+    private const RATE_LIMIT_MAX = 300;
     private const RATE_LIMIT_WINDOW = 60; // seconds
     private const ITEMS_PER_PAGE = 30;