feat: add structured logging with log/slog and panic recovery

Replace log.Printf/Println with slog.Info/Error/Warn across the codebase.
Initialize slog with JSON handler in main.go. Add panic recovery defer
in SSH session handler. Add structured game event logging (room created,
player joined, game started, game over, player inactive removed).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/ssh.go

@@ -2,7 +2,7 @@ package server
 
 import (
 	"fmt"
-	"log"
+	"log/slog"
 
 	"github.com/charmbracelet/ssh"
 	"github.com/charmbracelet/wish"
@@ -31,6 +31,14 @@ func Start(addr string, lobby *game.Lobby, db *store.DB) error {
 				if s.PublicKey() != nil {
 					fingerprint = gossh.FingerprintSHA256(s.PublicKey())
 				}
+
+				defer func() {
+					if r := recover(); r != nil {
+						slog.Error("session panic recovered", "error", r, "fingerprint", fingerprint)
+					}
+				}()
+
+				slog.Info("new SSH session", "fingerprint", fingerprint, "width", pty.Window.Width, "height", pty.Window.Height)
 				m := ui.NewModel(pty.Window.Width, pty.Window.Height, fingerprint, lobby, db)
 				return m, []tea.ProgramOption{tea.WithAltScreen()}
 			}),
@@ -40,6 +48,6 @@ func Start(addr string, lobby *game.Lobby, db *store.DB) error {
 		return fmt.Errorf("could not create server: %w", err)
 	}
 
-	log.Printf("Starting SSH server on %s", addr)
+	slog.Info("starting SSH server", "addr", addr)
 	return s.ListenAndServe()
 }