Add game deletion with authorization check

- Add Delete method to GameStore and Persister interface
- Add delete button to game list on home page
- Verify user owns game before allowing deletion
- Use status constants instead of magic numbers
- Remove unused variable in persister

db/persister.go

@@ -19,7 +19,7 @@ func NewGamePersister(q *gen.Queries) *GamePersister {
 func (p *GamePersister) SaveGame(g *game.Game) error {
 	ctx := context.Background()
 
-	existing, err := p.queries.GetGame(ctx, g.ID)
+	_, err := p.queries.GetGame(ctx, g.ID)
 	if err == sql.ErrNoRows {
 		_, err = p.queries.CreateGame(ctx, gen.CreateGameParams{
 			ID:          g.ID,
@@ -43,7 +43,6 @@ func (p *GamePersister) SaveGame(g *game.Game) error {
 		winningCells = sql.NullString{String: wc, Valid: true}
 	}
 
-	_ = existing
 	return p.queries.UpdateGame(ctx, gen.UpdateGameParams{
 		Board:        g.BoardToJSON(),
 		CurrentTurn:  int64(g.CurrentTurn),
@@ -124,3 +123,8 @@ func (p *GamePersister) LoadGamePlayers(gameID string) ([]*game.Player, error) {
 
 	return players, nil
 }
+
+func (p *GamePersister) DeleteGame(id string) error {
+	ctx := context.Background()
+	return p.queries.DeleteGame(ctx, id)
+}