v0.7.1 — English (UK) language switch

Switches the app's language from English (US) to English (UK).

• <html lang> set to en-GB.
• British spelling across all visible copy — web UI, domain KPI/phase text, Word/PPT export labels, and the capture-workbook headers: realized → realised, optimization → optimisation, modernization → modernisation, utilization → utilisation, dialog → dialogue. (The earlier en-ZA pass had fixed the noun "Realisation" but left the verb "realised".)
• Code identifiers, Auth.js callbacks, and the HTTP-401 "Unauthorized" reason phrase are intentionally unchanged.
• Capture-workbook import stays backward-compatible: header rows are matched positionally, so previously-downloaded and sample workbooks still import; a fallback reads either spelling for the one exact-match summary label.
• scripts/fix-org-name-realisation.mjs — renames any Organization whose name uses "Realization" → "Realisation" (the org name is what the sidebar logo renders). Run per-database.

Verified live on production (lang=en-GB + British copy on the sign-in page); org rename applied to prod.