[OPS] Manutenzione flag-gated: .htaccess (503→maintenance.html) + pagina + bypass token

Meccanismo riusabile: presenza di ../.maintenance (gitignored) → ogni richiesta 503 +
maintenance.html (mostra la finestra). Bypass ?mnt=<token>/cookie. Accendi: touch
.maintenance · Spegni: rm .maintenance. Attivato ora per il revamp UI V3 (~1h).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

public/.htaccess

@@ -1,5 +1,17 @@
 RewriteEngine On
 
+# ══════════════════════════════════════════════════════════════════════════
+# MANUTENZIONE (flag-gated): se esiste <docroot>/../.maintenance, OGNI richiesta
+# → HTTP 503 + maintenance.html. Bypass: ?mnt=<token> o cookie nis2_mnt=<token>.
+# Accendere: touch ../.maintenance  ·  Spegnere: rm ../.maintenance  (istantaneo)
+# ══════════════════════════════════════════════════════════════════════════
+ErrorDocument 503 /maintenance.html
+RewriteCond %{DOCUMENT_ROOT}/../.maintenance -f
+RewriteCond %{REQUEST_URI} !^/maintenance\.html$
+RewriteCond %{QUERY_STRING} !(^|&)mnt=efc088d042032889b64b887d2e562ec8(&|$)
+RewriteCond %{HTTP_COOKIE} !nis2_mnt=efc088d042032889b64b887d2e562ec8
+RewriteRule ^ - [R=503,L]
+
 # Pass Authorization header to PHP-FPM
 RewriteCond %{HTTP:Authorization} .+
 RewriteRule ^ - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]

public/maintenance.html

@@ -0,0 +1,33 @@
+<!DOCTYPE html>
+<html lang="it">
+<head>
+<meta charset="UTF-8">
+<title>NIS2 Agile — Manutenzione in corso</title>
+<meta name="viewport" content="width=device-width, initial-scale=1">
+<meta name="robots" content="noindex">
+<style>
+  *{box-sizing:border-box}
+  body{margin:0;min-height:100vh;display:flex;align-items:center;justify-content:center;
+       background:#0A2E54;color:#fff;font-family:system-ui,-apple-system,'Segoe UI',Roboto,Arial,sans-serif}
+  .box{max-width:540px;text-align:center;padding:44px 28px}
+  .logo{width:62px;height:62px;border-radius:15px;background:#1E8A5A;display:inline-flex;align-items:center;
+        justify-content:center;font-weight:800;font-size:21px;margin-bottom:20px}
+  h1{font-size:27px;margin:0 0 12px;letter-spacing:-.3px}
+  p{color:#cfe0f3;line-height:1.65;font-size:15px;margin:0 0 14px}
+  .win{display:inline-block;margin-top:10px;background:rgba(255,255,255,.10);border:1px solid rgba(255,255,255,.18);
+       border-radius:11px;padding:13px 20px;font-size:15px;line-height:1.5}
+  .win b{color:#F0B429}
+  .small{font-size:12.5px;color:#9db8d2;margin-top:24px}
+</style>
+</head>
+<body>
+  <div class="box">
+    <div class="logo">N2</div>
+    <h1>Manutenzione in corso</h1>
+    <p>Stiamo aggiornando l'<strong>interfaccia (UI)</strong> di NIS2 Agile su richiesta di modifica.
+       Il servizio non è momentaneamente accessibile.</p>
+    <div class="win">Finestra di manutenzione: <b>oggi dalle 10:39 alle ~11:45</b> (ora italiana)<br>durata stimata <b>circa 1 ora</b></div>
+    <p class="small">Grazie per la pazienza. Non occorre fare nulla: l'accesso tornerà disponibile automaticamente al termine.</p>
+  </div>
+</body>
+</html>