chore: initial commit - LoMines v3.0.0 base structure

- Java rewrite from Kotlin
- LoAPI 3.0.0 integration
- Paper 1.21 support
- Core mine system with handlers
- BlockSetter abstraction (Bukkit/Oraxen/ItemsAdder)
- Statistics and leaderboard system
- Group wand for batch mine creation
- Mask fill mode support

Known issues:
- ConfigLoader.java: 712 lines (needs refactoring)
- MineCommands.java: 341 lines (needs splitting)
- 7 classes exceed 200 line limit
- Code quality improvements needed (KISS, DRY, SOLID)

src/main/java/com/loki/lomines/gui/package-info.java

@@ -0,0 +1,13 @@
+/**
+ * GUI editors for mine configuration.
+ * <p>
+ * This package contains graphical user interface implementations using LoAPI's InventoryGUI:
+ * <ul>
+ *   <li>{@code MinesEditor} - List view of all mines</li>
+ *   <li>{@code MineEditor} - Main menu for a specific mine</li>
+ *   <li>{@code MineContentsEditor} - Editor for mine block contents</li>
+ *   <li>{@code MineRewardsEditor} - List view of mine rewards</li>
+ *   <li>{@code MineRewardEditor} - Editor for a specific reward</li>
+ * </ul>
+ */
+package com.loki.lomines.gui;