Replace System.err with file-backed AppLogger across all service layers

[Copilot]

Windows jpackage installs run as a pure GUI process — no console, so all System.err/System.out output is silently dropped. Every unhandled exception in the service layer killed the app with zero user feedback.

Changes

• util/AppLogger (new): single static logger writing timestamped entries to both stderr and ~/.namegame/namegame.log (fallback: %TEMP%\namegame.log). Call init(Path) once at startup; use log(String) / log(String, Throwable) everywhere else.

• NameGameApplication: removed duplicated logging fields/methods; delegates to AppLogger. main() calls AppLogger.init() before any service is instantiated or the FX toolkit is launched.

• SoundService, ImageService, RosterService, MappingService, StatisticsService: all System.err.println() / System.out.println() calls replaced with AppLogger.log().

• .github/copilot-instructions.md: added Logging and Error Handling sections codifying AppLogger as the required pattern and explicitly prohibiting direct console output.

// Before (silently lost in GUI installs)
System.err.println("Failed to load roster: " + e.getMessage());

// After (written to ~/.namegame/namegame.log regardless of console)
AppLogger.log("Failed to load roster: " + rosterFile, e);

Original prompt

Try again

The user has attached the following file paths as relevant context:

• .github\copilot-instructions.md

Created from VS Code.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.