[WIP] Extend pricing system to support item-based min and max prices

[Copilot]

Plan: Add Item-Based Min/Max Price Support

• Explore the codebase and understand current pricing logic
• Add global min-price and max-price to config.yml with decimal support
• Add per-item price configuration structure to config.yml
• Create PriceConfig utility class for loading and validating prices
• Add price formatting utility using BigDecimal
• Update Settings.java to load global min/max prices
• Update NewOrderMenu.java to validate prices against min/max
• Add random price generation with decimal support
• Update language files with new validation messages
• Test price validation and formatting
• Run build to ensure no compilation errors

Original prompt

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This section details on the original issue you should resolve

<issue_title>✨ Set up Copilot instructions</issue_title>
<issue_description>Extend the pricing system to support item-based min-price and max-price with decimal values.

Requirements:

• Support decimal (double / BigDecimal) min-price and max-price per item.
• Prices must be read from config.yml and support both integer and decimal values.
• Global min-price and max-price must still exist as fallback defaults.
• If an item has its own min/max defined, use those values instead of global ones.
• Validate per-item prices:
  • min-price <= max-price
  • if invalid or missing, fallback to global min/max and log a warning.
• Do not break existing configs that only define global prices.
• Random price generation must work with decimal values.
• Format prices to 2 decimal places when displayed to players.
• Prefer BigDecimal for all price calculations (Vault economy compatibility).
• Avoid runtime exceptions caused by malformed config values.

Context:

• Language: Java
• Platform: Spigot / Paper Minecraft plugin
• Config: YAML (config.yml)
• Economy: Vault

Please provide:

• Updated config.yml example (global + item-based prices)
• Java code to load and validate prices
• Price resolution logic (item override → global fallback)
• Random decimal price generation implementation
• Utility method for formatting prices

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes NotPatch/NOrder#8

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