fix: TTS test ask user if heard + PHP 8 end() ref bug + DB migration guard for fresh volumes

- app.js: TTS kiosk timeout 4s → 10s; fires interactive 'Hai sentito?' YES/NO
  prompt instead of showing error (TTS can take 6-8s; UtteranceProgressListener
  may not fire on all firmware); YES → success, NO → troubleshooting steps
- translations: add heard_question/heard_yes/heard_no/test_ok_kiosk/test_fail_steps
  to all 5 languages (it/en/de/fr/es) under settings.tts
- api/index.php: fix end() PHP 8.0+ reference error in _offFetchProduct()
  (categories_hierarchy stored in temp var before calling end())  (fixes #130)
- api/database.php: migrateDB() now checks sqlite_master for 'products' table;
  if missing, calls initializeDB() and returns — no ALTER on nonexistent table
  (fixes #133, covers #131)
- api/index.php: health_check db_row_count query guarded against missing
  inventory table (fixes #131)

api/database.php

@@ -126,6 +126,16 @@ function initializeDB(PDO $db): void {
 }
 
 function migrateDB(PDO $db): void {
+    // Guard: if core tables don't exist yet (e.g. DB file present but empty / partial init),
+    // run initializeDB first so all tables are created, then return — no ALTER TABLE needed.
+    $productsExists = $db->query(
+        "SELECT name FROM sqlite_master WHERE type='table' AND name='products'"
+    )->fetchColumn();
+    if (!$productsExists) {
+        initializeDB($db);
+        return;
+    }
+
     // Add package_unit column if missing
     $cols = $db->query("PRAGMA table_info(products)")->fetchAll();
     $colNames = array_column($cols, 'name');