Stage 15 — PWA complete: install prompt + Web Push notifications

Dependency:
- minishlink/web-push v10 (VAPID JWT + aes128gcm payload encryption)
- Dockerfile: add curl, mbstring, gmp extensions (web-push needs ext-curl)

VAPID:
- config/webpush.php from env; `php artisan push:vapid` generates keypair
- Shared platform keypair; .env.example has empty placeholders

Schema:
- push_subscriptions (user/company, endpoint unique, p256dh, auth, encoding)

WebPushService:
- send / sendToUser / dispatch via WebPush::flush
- Auto-prunes subscriptions reported expired (404/410)

Subscribe flow:
- POST /push/subscribe + /push/unsubscribe (auth, tenant)
- Tenant panel JS subscribes after SW registration with VAPID public key

Service worker (/sw.js):
- Cache v2, push listener → showNotification, notificationclick → focus/open

Install prompt:
- Floating "Instalează aplicația" button wired to beforeinstallprompt

Staff push:
- WorkOrder master_id change → push to assigned mechanic
- Settings "Test notificare push" action

Tests (6 new):
- subscribe stores + upserts; requires auth (401); validation (422);
  service configured; sendToUser with no subs returns zero

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

composer.json

@@ -15,6 +15,7 @@
         "laravel/reverb": "^1.10",
         "laravel/sanctum": "^4.3",
         "laravel/tinker": "^2.10.1",
+        "minishlink/web-push": "^10.0",
         "spatie/laravel-activitylog": "^5.0",
         "spatie/laravel-medialibrary": "^11.22",
         "spatie/laravel-permission": "^7.4",