feat: implement i18n support and add Japanese localization

[ariela]

This Pull Request introduces a lightweight internationalization (i18n) framework to the Alchemy Factory Calculator, along with full support for the Japanese language. It also includes a significant refactor of the UI logic to support dynamic localization.

Key Changes

1. I18n Framework (alchemy_i18n.js)
   • Implemented a lightweight translation module that uses English keys as the source.
   • Supports dynamic dictionary loading via script tags to ensure compatibility with the file:// protocol (no CORS issues).
   • Persists language preference in localStorage.
2. Japanese Localization (lang/ja.js)
   • Added a comprehensive translation dictionary for all items, machines, UI labels, and warning messages.
3. UI & Tooltip Refactoring
   • Replaced hardcoded strings in alchemy_calc.js and alchemy_ui.js with I18n.t() calls.
   • Refactored tooltip generation logic to be more modular and localization-friendly.
   • Added data-i18n attributes to index.html for static text management.
4. Multilingual Search & UX Improvements
   • Enhanced the search logic for items and recipes to match both internal English keys and localized display names.
   • Added a language selector in the header for seamless switching without page reloads.
5. Logistics & Status Localization
   • Localized dynamic labels such as belt load ratios (e.g., Full Belt, ~75% Load) and production status messages.

Technical Notes

• Fallback Mechanism: The system defaults to the English key if a translation is missing, ensuring no broken UI elements.
• Extensibility: The architecture is designed to make adding future languages as simple as dropping a new file in the lang/ directory.