feat(pwa): add web share target for text and images with offline queue

frontend/public/manifest.json

@@ -47,6 +47,22 @@
       "purpose": "maskable"
     }
   ],
+  "share_target": {
+    "action": "/share-target",
+    "method": "POST",
+    "enctype": "multipart/form-data",
+    "params": {
+      "title": "title",
+      "text": "text",
+      "url": "url",
+      "files": [
+        {
+          "name": "media",
+          "accept": ["image/*"]
+        }
+      ]
+    }
+  },
   "shortcuts": [
     {
       "name": "Gedanke sofort erfassen",