feat: Add file-based trade logging system and preview command

[hudsonandres]

➜ Added a comprehensive file-based logging system for trades and a preview command to test GUI layouts without requiring a second player account.

General explain:

🆕 Feat 1: File-Based Trade Logging

Implementation

A singleton logger that writes trade events to daily text files using an asynchronous queue system.

Key Features:

• Daily log files: logs/yyyy-MM-dd.txt format
• Async processing: Non-blocking writes using BlockingQueue (100 entry buffer)
• Auto-flush: 1-second intervals to ensure data persistence
• Graceful shutdown: Flushes remaining queue entries on server stop
• Configurable filters: Control exactly what gets logged

Log Entry Format:

• dd/MM/yyyy HH:mm:ss - EVENT_TYPE - Details

Configuration

Added to Config.yml:

TradeLog:
  log-trade-files: false           # Master switch for file logging
  log-filters:                     # Granular control
    log-trade-started: false       # When trade begins
    log-trade-finished: false      # Successful completion
    log-trade-cancelled: false     # Cancellation + reason
    log-items-offered: false       # Item placement events
    log-items-received: false      # Final item distribution

Integration Points

• TradeLogService: Calls FileTradeLogger.log() for all trade events
• TradeSystem: Shutdown hook ensures proper queue flushing
• Works independently from existing database logging

🆕 Feat 2: Preview Command

Implementation

Extends the Trade class to create a single-player preview mode for testing GUI layouts.

How it works:

• Opens trade GUI for one player only
• Simulates trade environment without actual trading
• Prevents normal trade completion
• Isolated from regular trade flow

Command Usage:
/trade preview

Permission: TradeSystem.Trade.Preview

Technical Details 📊

Performance

• Async logging: No impact on main server thread
• Queue buffering: Prevents I/O bottlenecks
• Scheduled flushing: Batches writes for efficiency

Error Handling

• Silent failure mode (logged to console only)
• Queue overflow protection
• Thread-safe implementation

File Management

• Automatic date rollover at midnight
• Creates logs/ directory if missing
• UTF-8 encoding for international characters