feat(gyms): show gym logos in navbar buttons and brand; accept JPEG XL uploads

.htaccess

@@ -1,6 +1,11 @@
 # Disable directory listing
 Options -Indexes
 
+# JPEG XL uploads (gym header/logo): older mime.types don't know the extension.
+<IfModule mod_mime.c>
+    AddType image/jxl .jxl
+</IfModule>
+
 # Block direct HTTP access to sensitive files
 <FilesMatch "^\.(env|env\..*|git.*|htaccess|htpasswd)$">
     Require all denied