feat: initialize sensors database table and index on server startup

realtime/src/helper/authdb.js

@@ -19,6 +19,25 @@ async function checkDB() {
     }
 }
 
+async function initDB() {
+    try {
+        await pool.query(`
+            CREATE TABLE IF NOT EXISTS sensors (
+                id VARCHAR(10) PRIMARY KEY,
+                name VARCHAR(100) NOT NULL,
+                code_hash TEXT NOT NULL UNIQUE,
+                is_active BOOLEAN DEFAULT TRUE,
+                last_seen TIMESTAMP DEFAULT NOW(),
+                created_at TIMESTAMP DEFAULT NOW()
+            );
+            CREATE INDEX IF NOT EXISTS idx_sensors_code_hash ON sensors(code_hash);
+        `);
+        console.log('[DB] Database schema initialized (sensors table ensured)');
+    } catch (error) {
+        console.error('[DB] Schema initialization failed:', error);
+    }
+}
+
 /**
  * Restituisce i dati del sensore in base al token ricevuto.
  * Il token viene hashato prima della comparazione con il database.