[Feat] Admin GUI: Runtime Config Editor #40

Summary

The AdminConfigPage currently displays a "Coming Soon" placeholder. Implement a runtime configuration editor GUI that allows admins to view and modify plugin settings without editing files manually.

Features

Config Display

• List all config sections with current values
• Group settings by category (general, economy, combat, territory, etc.)
• Show setting descriptions and default values
• Indicate which settings require a reload vs. take effect immediately

Editing

• Editable fields for each config value (text fields, checkboxes, sliders, dropdowns as appropriate)
• Input validation (numeric ranges, string patterns, enum values)
• Highlight modified values that differ from defaults

Actions

• Save — Write changes to config file
• Reload — Reload config from disk (discard in-memory changes)
• Reset to Default — Reset individual settings or entire sections
• Save & Reload — Write and apply changes in one action

Scope

Should cover:

• Main config.json settings
• Module-specific configuration sections
• Zone flag defaults
• Economy settings (currency, tax rates, upkeep)

Existing Infrastructure

• AdminConfigPage.java — Placeholder page exists
• ConfigManager — Handles config loading/saving
• Admin GUI framework — Fully functional for other admin pages

Origin

Roadmap Phase B.3 ("Coming Soon" admin page placeholder).