ui(ucp): placeholder generique en francais sur la connexion UCP

ucp/index.php

@@ -150,7 +150,7 @@ $csrfToken   = UcpAuth::getCsrfToken();
                 <div>
                     <label for="ucp-login-user" class="block text-xs font-semibold text-slate-700 mb-1.5">Identifiant utilisateur</label>
                     <input type="text" id="ucp-login-user" name="username" required autocomplete="username" autofocus
-                        placeholder="ex: fred ou fred@entreprise.fr"
+                        placeholder="Votre identifiant"
                         class="w-full px-3.5 py-2.5 rounded-xl bg-slate-50 border border-slate-300 text-base sm:text-sm text-slate-900 focus:bg-white focus:ring-2 focus:ring-indigo-500/30 focus:border-indigo-500 focus:outline-none transition">
                 </div>
                 <div>