Add user authentication and game persistence with SQLite

- User registration/login with bcrypt password hashing
- SQLite database with goose migrations and sqlc-generated queries
- Games and players persisted to database, resumable after restart
- Guest play still supported alongside authenticated users
- Auth UI components (login/register forms, auth header, guest banner)

ui/lobby.go

@@ -4,9 +4,17 @@ import (
 	"github.com/ryanhamamura/via/h"
 )
 
-func LobbyView(nicknameBind, createGameKeyDown, createGameClick h.H) h.H {
+func LobbyView(nicknameBind, createGameKeyDown, createGameClick h.H, isLoggedIn bool, username string, logoutClick h.H) h.H {
+	var authSection h.H
+	if isLoggedIn {
+		authSection = AuthHeader(username, logoutClick)
+	} else {
+		authSection = GuestBanner()
+	}
+
 	return h.Main(h.Class("container"),
 		h.Div(h.Class("lobby"),
+			authSection,
 			h.H1(h.Text("Connect 4")),
 			h.P(h.Text("Challenge a friend to a game of Connect 4!")),
 			h.Form(