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

manifest.json

@@ -2,7 +2,7 @@
     "name": "EverShelf",
     "short_name": "EverShelf",
     "description": "Gestione completa della dispensa di casa con scansione barcode",
-    "version": "1.7.8",
+    "version": "1.7.9",
     "start_url": "/evershelf/",
     "display": "standalone",
     "background_color": "#f0f4e8",