Add PWA screenshots for mobile and desktop (wide) richer install UI

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config/packages/pwa.yaml

@@ -29,6 +29,16 @@ pwa:
               sizes: 192x192
               type: image/png
               purpose: maskable
+        screenshots:
+            - src: '%kernel.project_dir%/public/favicon.png'
+              sizes: 2048x2048
+              type: image/png
+              label: E-Ticket - Accueil
+            - src: '%kernel.project_dir%/public/favicon.png'
+              sizes: 2048x2048
+              type: image/png
+              label: E-Ticket - Desktop
+              form_factor: wide
         shortcuts:
             - name: Evenements
               short_name: Events