Add 'Add to contacts' feature

Toolbar More menu now saves sender to Contact Manager with green
success toast or grey 'Already in contacts' toast for duplicates.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/launch.json

@@ -0,0 +1,11 @@
+{
+  "version": "0.0.1",
+  "configurations": [
+    {
+      "name": "dashmail",
+      "runtimeExecutable": "npx",
+      "runtimeArgs": ["serve", "-p", "3000", "."],
+      "port": 3000
+    }
+  ]
+}