feat(FR-1567): add i18n configuration for Storybook

[limshyun]

Resolves #4416(FR-1567)

Summary

• Add i18n configuration for Storybook with 21 supported languages
• Add locale selector toolbar in Storybook to switch languages dynamically
• Add i18next dependencies for Storybook development

Changes

• packages/backend.ai-ui/src/i18n.ts: New i18n configuration that imports all locale files directly
• packages/backend.ai-ui/.storybook/preview.tsx: Add i18n decorator with locale selector toolbar
• packages/backend.ai-ui/package.json: Add i18next-browser-languagedetector and i18next-http-backend as devDependencies

Supported Languages

English, Korean, Japanese, Chinese (Simplified/Traditional), German, French, Spanish, Portuguese, Italian, Russian, Polish, Greek, Finnish, Turkish, Thai, Vietnamese, Indonesian, Malay, Mongolian

Test Plan

• Run Storybook and verify locale selector appears in toolbar
• Switch between languages and verify translations update in components using useTranslation

2026-01-06.2.49.53.mov

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[limshyun]

• feat(FR-1567): add i18n configuration for Storybook #4946 👈 (View in Graphite)
• main

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[github-actions]

Coverage report for ./packages/backend.ai-ui

St.❔	Category	Percentage	Covered / Total
🟡	Statements	63.5%	254/400
🔴	Branches	42.3%	151/357
🔴	Functions	50%	46/92
🟡	Lines	65.16%	230/353

Show new covered files 🐣

St.❔	File	Statements	Branches	Functions	Lines
🔴	... / BAIDomainSelector.tsx	50%	0%	0%	50%

Test suite run success

186 tests passing in 9 suites.

Report generated by 🧪jest coverage report action from 492a193

[Copilot]

Pull request overview

This PR adds i18n (internationalization) configuration for Storybook to enable locale switching in component stories. It introduces a new i18n configuration file, adds a locale selector toolbar in Storybook, and includes two i18next plugin dependencies.

Key changes:

• New i18n configuration specifically for Storybook with all 21 locale files imported directly
• Storybook decorator with locale selector toolbar supporting language switching
• Addition of i18next-browser-languagedetector and i18next-http-backend as dev dependencies

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.

File	Description
packages/backend.ai-ui/src/i18n.ts	New i18n configuration file that imports all 21 locale JSON files and initializes a separate i18n instance for Storybook
packages/backend.ai-ui/.storybook/preview.tsx	Adds i18n decorator with locale switching and toolbar configuration for 21 supported languages
packages/backend.ai-ui/package.json	Adds two i18next plugins as devDependencies
pnpm-lock.yaml	Auto-generated lock file updates for new dependencies

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

[nowgnuesLee]

LGTM