feat(api): add account workspaces and signed content events

server/src/WebDrop.Api/ApiContract.cs

@@ -2,6 +2,7 @@ namespace WebDrop.Api;
 
 public static class ApiContract
 {
+    // v5 changes channel capacity from per-endpoint devices to account members.
     // Keep this aligned with contracts/api-contract.json and docs/openapi.yaml.
-    public const string Version = "2.1.0";
+    public const string Version = "6.0.0";
 }