[Feature] Add internationalization support

[coderabbitai]

Overview

Prepare ThumbCode for international markets with i18n support.

Current State

• All text hard-coded in English
• No i18n infrastructure
• No translation process

Requirements

• Choose and integrate i18n library (react-i18next)
• Extract all strings to translation files
• Support languages: English, Spanish, French, German, Japanese, Chinese (Simplified)
• Implement language switcher
• Add RTL support
• Handle date/time and number formatting
• Create translation workflow
• Add context for translators
• Test all languages
• Document i18n process

Success Criteria

• 6+ languages supported
• Easy to add new languages
• No hard-coded strings
• RTL support working

Priority: LOW

Estimated Effort: 5-6 days

Labels: feature, i18n, priority:low

Backlink: Related to PR #2

[jbdevprimary]

Closing — internationalization is a post-v1.0 feature. Current considerations:

• All UI text is in English; extraction to i18n files would touch every component
• react-i18next integration is straightforward but needs translation workflow
• RTL support requires layout changes across all pages
• The BYOK model means users are global — i18n is important but not a v1.0 blocker

When ready to implement, start with: (1) Install react-i18next, (2) Extract strings from pages/components, (3) Set up translation file structure, (4) Add language switcher to settings.