perf(db): eliminate redundant DDL execution on every request and add nexus-cluster to update.sh sudoers

src/Database.php

@@ -29,7 +29,7 @@ class Database
                 mkdir($dir, 0770, true);
             }
 
-            $isNew = !file_exists(self::DB_PATH);
+            $isNew = !file_exists(self::DB_PATH) || filesize(self::DB_PATH) === 0;
 
             self::$instance = new PDO('sqlite:' . self::DB_PATH, null, null, [
                 PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
@@ -41,10 +41,17 @@ class Database
             self::$instance->exec('PRAGMA journal_mode = WAL;');
             self::$instance->exec('PRAGMA busy_timeout = 5000;');
 
-            self::initializeSchema();
-
             if ($isNew) {
+                self::initializeSchema();
                 @chmod(self::DB_PATH, 0660);
+            } else {
+                // Si la base existe déjà, éviter d'exécuter l'intégralité du DDL à chaque requête HTTP
+                // ce qui sature SQLite de verrous exclusifs inutiles. On teste juste l'existence de la table principale.
+                try {
+                    self::$instance->query("SELECT 1 FROM settings LIMIT 1");
+                } catch (\Throwable $e) {
+                    self::initializeSchema();
+                }
             }
         }