core: support SMP basic auth / server password (#1358)

src/Simplex/Chat/Migrations/chat_schema.sql

@@ -384,6 +384,7 @@ CREATE TABLE smp_servers(
   user_id INTEGER NOT NULL REFERENCES users ON DELETE CASCADE,
   created_at TEXT NOT NULL DEFAULT(datetime('now')),
   updated_at TEXT NOT NULL DEFAULT(datetime('now')),
+  basic_auth TEXT,
   UNIQUE(host, port)
 );
 CREATE INDEX idx_messages_shared_msg_id ON messages(shared_msg_id);