Add play again button for rematch after game ends

When a game finishes (win or draw), players see a "Play again" button.
Clicking it creates a new game and the opponent sees a "Join Rematch"
link to join the same game.

ui/status.go

@@ -5,7 +5,7 @@ import (
 	"github.com/ryanhamamura/via/h"
 )
 
-func StatusBanner(g *game.Game, myColor int) h.H {
+func StatusBanner(g *game.Game, myColor int, playAgainClick h.H) h.H {
 	var message string
 	var class string
 
@@ -35,10 +35,34 @@ func StatusBanner(g *game.Game, myColor int) h.H {
 		class = "status draw"
 	}
 
-	return h.Div(
+	content := []h.H{
 		h.Class(class),
 		h.Text(message),
-	)
+	}
+
+	// Show rematch options for finished games
+	if g.IsFinished() {
+		if g.RematchGameID != nil {
+			content = append(content,
+				h.A(
+					h.Class("rematch-link"),
+					h.Href("/game/"+*g.RematchGameID),
+					h.Text("Join Rematch"),
+				),
+			)
+		} else if playAgainClick != nil {
+			content = append(content,
+				h.Button(
+					h.Class("play-again-btn"),
+					h.Type("button"),
+					h.Text("Play again"),
+					playAgainClick,
+				),
+			)
+		}
+	}
+
+	return h.Div(content...)
 }
 
 func getOpponentName(g *game.Game, myColor int) string {