feat: v1.7.9 — category badges, category search, AI guards

- Category badge on every inventory item (icon + label); 'altro' items
  refined asynchronously via new guess_category Gemini endpoint
  (data/category_ai_cache.json) — no AI call when key not configured
- Category search: inventory search now matches by macro-category key
  and translated label (e.g. 'biscotti' finds all cookie items)
- Brand fast-path in guessCategoryFromName (Oreo, Barilla, Lavazza…)
- Fix: duplicate banner alerts — _bannerLoading guard + _queuedItemIds Set
- Fix: mapToLocalCategory with en:dairies (dairi stem added)
- Fix: mapToLocalCategory no longer blocks on 'altro' — falls back to
  guessCategoryFromName(productName) before returning 'altro'
- Fix: 'Tonno all'olio' was resolving to condimenti — moved tonno\b
  check before olio\b in conserve regex block
- AI guards: _refineCategoryBadgesAsync and fetchAllPrices now check
  _geminiAvailable (JS); getShoppingPrice returns no_api_key (PHP)
  when GEMINI_API_KEY is not set — all AI functions are now explicit

api/index.php

@@ -17,6 +17,7 @@ define('_GH_TK_ENC', '23580718460c2c444031290243627e7971622b29030a3e4d50001e4526
 define('_GH_TK_KEY', 'D1sp3ns4!Ev3r#26');
 define('GH_REPO',    'dadaloop82/EverShelf');
 define('PRICE_CACHE_PATH', __DIR__ . '/../data/shopping_price_cache.json');
+define('CATEGORY_CACHE_PATH', __DIR__ . '/../data/category_ai_cache.json');
 
 /** Decode the XOR-obfuscated GitHub token at runtime. */
 function _ghToken(): string {
@@ -99,6 +100,12 @@ if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
     exit;
 }
 
+// ── Ping / heartbeat — early response, no DB or rate-limit required ───────────
+if (($_GET['action'] ?? '') === 'ping') {
+    echo json_encode(['ok' => true, 'ts' => time()]);
+    exit;
+}
+
 // ===== RATE LIMITING =====
 /**
  * Simple file-based rate limiter.
@@ -455,6 +462,10 @@ try {
             getAllShoppingPrices($db);
             break;
 
+        case 'guess_category':
+            guessCategoryFromAI();
+            break;
+
         default:
             http_response_code(404);
             echo json_encode(['error' => 'Unknown action: ' . $action]);
@@ -7393,6 +7404,59 @@ PROMPT;
     return $out;
 }
 
+/**
+/**
+ * GET /api/?action=guess_category&name=...
+ * Returns the macro-category for a product name, using a file cache + Gemini AI fallback.
+ * Response: { category: string }
+ */
+function guessCategoryFromAI(): void {
+    $name = trim($_GET['name'] ?? '');
+    if ($name === '') { echo json_encode(['category' => 'altro']); return; }
+
+    // Load cache
+    $cache = [];
+    if (file_exists(CATEGORY_CACHE_PATH)) {
+        $cache = json_decode(file_get_contents(CATEGORY_CACHE_PATH), true) ?? [];
+    }
+    $key = md5(mb_strtolower($name));
+    if (isset($cache[$key])) { echo json_encode(['category' => $cache[$key]]); return; }
+
+    $apiKey = env('GEMINI_API_KEY', '');
+    if ($apiKey === '') { echo json_encode(['category' => 'altro']); return; }
+
+    $cats   = 'latticini, carne, pesce, frutta, verdura, pasta, pane, surgelati, bevande, condimenti, snack, conserve, cereali, igiene, pulizia, altro';
+    $prompt = "Sei un classificatore di prodotti alimentari e domestici italiani.\n"
+            . "Classifica il prodotto \"" . addslashes($name) . "\" in UNA di queste categorie esatte: $cats.\n"
+            . "Rispondi con SOLO la parola chiave della categoria, senza spiegazioni né punteggiatura aggiuntiva.";
+
+    $payload = [
+        'contents'           => [['parts' => [['text' => $prompt]]]],
+        'generationConfig'   => [
+            'temperature'   => 0,
+            'maxOutputTokens' => 20,
+            'thinkingConfig'  => ['thinkingBudget' => 0],
+        ],
+    ];
+
+    $result = callGeminiWithFallback($apiKey, $payload, 10);
+    $raw    = strtolower(trim($result['data']['candidates'][0]['content']['parts'][0]['text'] ?? ''));
+    $raw    = preg_replace('/[^a-z_ ]/', '', $raw);
+    $raw    = trim($raw);
+
+    $valid  = ['latticini','carne','pesce','frutta','verdura','pasta','pane','surgelati',
+               'bevande','condimenti','snack','conserve','cereali','igiene','pulizia','altro'];
+    $cat    = in_array($raw, $valid, true) ? $raw : 'altro';
+
+    // Persist to cache
+    $cache[$key] = $cat;
+    @file_put_contents(CATEGORY_CACHE_PATH, json_encode($cache, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE));
+
+    echo json_encode(['category' => $cat]);
+}
+
+// ─────────────────────────────────────────────────────────────────────────────
+
 /**
  * GET /api/?action=get_shopping_price
  * POST body: { name, quantity, unit, default_quantity, package_unit, country, currency, lang, force_refresh }
@@ -7417,6 +7481,12 @@ function getShoppingPrice(PDO $db): void {
         return;
     }
 
+    // Guard: price estimation requires Gemini API key
+    if (empty(env('GEMINI_API_KEY'))) {
+        echo json_encode(['success' => false, 'error' => 'no_api_key']);
+        return;
+    }
+
     $cache = _loadPriceCache();
     $key   = _priceKey($name, $country);
     $now   = time();