Add managed server profiles and account login

docs/api-dotnet.md

@@ -96,6 +96,18 @@ Only explicit `Pin` or `Remove` changes the file. Pin replacement requires an
 explicit caller decision; malformed files fail closed. Changes replace the file
 atomically before updating memory. Use one owner per store/file.
 
+`ServerProfile` is the app-facing saved-server model shared by platform clients. Construct
+profiles with `ServerProfile.Create`, which trims values and requires a host, nonzero port,
+and username for account authentication. A profile contains only its stable ID, endpoint,
+authentication mode, username or guest nickname. It deliberately has no password field.
+Platform clients own any secret storage, such as macOS Keychain integration.
+
+`ServerProfileStore` serializes profiles as camel-case JSON with string authentication
+values. Missing, malformed and unreadable files load as an empty list; invalid individual
+profiles are discarded. Saving filters invalid entries and replaces the file through a
+same-directory temporary file. Use one owner per store/file and do not treat it as a
+credential store.
+
 `ServerIdentity` reads and writes the native 96-byte Ed25519 format:
 `public-key[32] || seed[32] || public-key[32]`. Loading verifies both public-key
 copies against the seed. Disposal clears the owned seed.