GH-139 Major codebase overhaul improving architecture, performance, and maintainability

[imDMK]

Description

This PR delivers a full, project-wide overhaul of the plugin.
It redesigns the architecture, boosts performance, simplifies internals, enhances maintainability, and introduces a complete modern API layer.
It also adds full modular database support and significantly reduces operational overhead.

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🔧 Architecture & Code Quality

• Fully refactored project structure for clarity and maintainability.
• Migrated to dependency injection via the PandaLang Injector.
• Rewritten service layer, repository layer, module lifecycle, and task scheduling.
• Introduced clear API / implementation separation.
• Added new utility subsystems:
  • time formatting
  • placeholders
  • adventure component utilities
  • validation
  • caching
  • scheduler abstractions

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⚡ Performance Enhancements

• Converted heavy operations to async where safe.
• Implemented Caffeine-based caching for user aggregates.
• Added memory-based top-users cache to avoid repeated DB aggregation.
• Improved thread-safety; reduced synchronization overhead.
• Removed redundant logic and streamlined core service calls.

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💾 Database Support

Added full support for major SQL engines:

• H2 (embedded)
• MySQL
• SQLite
• MariaDB
• PostgreSQL
• Microsoft SQL Server

Additional improvements:

• Dynamic JDBC driver loading → smaller JAR
• Rebuilt ORMLite repository layer with async pipelines & clean error handling

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🧹 JAR Size & Runtime Optimization

• Removed bundled drivers (loaded on demand)
• Reduced unused code and dependencies
• Improved class layout and module structure

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🎨 New API & Developer Experience

• Introduced a clean, modern public API layer.
• Added:
  • UserSaveReason
  • PluginTask
  • high-level abstractions for scheduling and user operations
• Improved User, UserService, and repository interfaces.

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🕒 Duration Formatting Improvements

• Added multiple formatting styles:
  • COMPACT, LONG, LONG_WITH_AND, NATURAL
• Introduced full formatting & conversion utilities.
• Strict validation + normalization.

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🧮 Top Users Cache

• Added TopUsersCache for instant leaderboard lookups.
• Configurable expiration and limits.
• Consistent invalidation strategy.

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🏷️ Project Rename

• Renamed plugin: SpentTime → AdvancedPlayTime
• Updated:
  • packages
  • config files
  • plugin metadata
  • public API references

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Result

• Smaller JAR
• Faster runtime
• Cleaner architecture
• Extensible DB layer
• Production-grade performance

Fixes: #108

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Have the changes been tested?

• Yes
• No