Internationalisation (i18n) #24

All UI text is hardcoded English. Adding i18n support enables Welsh-medium schools, Irish language schools, and eventually broader adoption.

Phase 1 — Framework:

• Add next-intl or similar
• Extract all UI strings to locale files (en-GB.json)
• Language picker in admin settings

Phase 2 — UK Languages:

• Welsh (cy), Irish (ga), Scottish Gaelic (gd)
• Speech synthesis: check browser support per language

Phase 3 — European:

• French, Spanish (most common UK school languages)

Note: Spelling game content (word lists) is always in the target language — only UI chrome needs translating.