feat: implement i18n support with Japanese and English languages

[nukopy]

Implements internationalization support for the blog site as requested in issue #3.

Changes

• Add language switcher next to theme switcher in header
• Implement language-prefix routing (/ for ja, /en/ for en)
• Restructure content files into language directories
• Create English route components for all pages
• Update Content Collections configuration for multi-language support

Technical Details

• Uses remix-i18next for i18n implementation
• Language detection from URL path with Japanese as default
• Content files organized in app/contents/ja/ and app/contents/en/
• Translation files in public/locales/

Closes #3

Generated with Claude Code

[nukopy]

@claude routes 配下のファイルは ja / en で共通です。
言語ごとのファイルは必要ないように動的にパスを書き換えるように実装して。

[claude]

Claude finished @nukopy's task —— View job

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Refactoring i18n implementation to use dynamic routing ✅

Successfully refactored the i18n implementation to eliminate duplicate route files and use dynamic path rewriting.

Todo List

• Analyze current route structure and i18n implementation
• Remove English-specific route files under /en/ directory
• Update main route components to handle both languages dynamically
• Modify routing configuration for dynamic language handling
• Test the implementation with both Japanese and English paths
• Run quality checks (typecheck, lint, etc.)
• Commit and push changes

Changes Made

1. Removed Duplicate Route Files

• Deleted all English-specific route files in app/routes/en/ directory
• Eliminated 6 duplicate component files (contents.tsx, contents.$slug.tsx, home.tsx, layout.tsx, tags.tsx, tags.$tag.tsx)

2. Updated Route Configuration

• Modified app/routes.ts to reuse the same components for both language paths
• English routes now use undefined layout and reference the main components

3. Enhanced Route Components

• All loaders now detect language from request.url using url.pathname.startsWith("/en")
• Dynamic URL generation: Each component builds language-aware URLs using helper functions
• Consistent language handling: Japanese (default) uses / prefix, English uses /en/ prefix

4. Updated Components

• contents.tsx: Language-aware content listing and tag links
• contents.$slug.tsx: Dynamic breadcrumbs and navigation with language detection
• home.tsx: Language-aware navigation buttons
• tags.tsx: Language-aware tag links and navigation
• tags.$tag.tsx: Language-aware content and navigation links
• I18nProvider.tsx: Added language context hook for future use

Technical Implementation

The solution maintains the existing URL structure:

• Japanese (default): /, /contents, /contents/slug, /tags, /tags/tag
• English: /en/, /en/contents, /en/contents/slug, /en/tags, /en/tags/tag

But now uses a single set of components that dynamically:

1. Detect language from the request URL in loaders
2. Load appropriate language content using getContentsByLanguage(language)
3. Generate proper URLs for navigation links based on current language

This reduces code duplication significantly (removed 449 lines, added 93) while maintaining full i18n functionality.

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Job Run: https://github.com/nukopy/chasing-the-kernel.com/actions
Branch: claude/issue-3-20250901-0916