PWA: install button, one icon badge for Signal, mail and tasks due, share target for files, manifest launch handler

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/manifest.webmanifest

@@ -91,5 +91,28 @@
         }
       ]
     }
-  ]
+  ],
+  "dir": "ltr",
+  "prefers_related_applications": false,
+  "launch_handler": {
+    "client_mode": [
+      "navigate-existing",
+      "auto"
+    ]
+  },
+  "share_target": {
+    "action": "/share-target",
+    "method": "POST",
+    "enctype": "multipart/form-data",
+    "params": {
+      "files": [
+        {
+          "name": "files",
+          "accept": [
+            "*/*"
+          ]
+        }
+      ]
+    }
+  }
 }