feat(i18n): ship CJK and FIGS locales alongside English

[iAstro]

What this adds

Seven translated bundles on top of the existing English and Simplified Chinese: zh-TW, ja, ko, fr, it, de, es. The UI now follows the browser language across the major markets instead of falling back to Chinese (#168) or, after #174, to English only.

Resource keys

Bare language subtags for the new languages, so regional variants share one bundle:

Browser language	Resource
en*	en-US
zh-Hans*, zh-CN, zh-SG, zh	zh-CN
zh-Hant*, zh-TW, zh-HK, zh-MO	zh-TW
ja, ja-JP	ja
ko, ko-KR	ko
fr, fr-FR, fr-CA	fr
it, it-IT	it
de, de-DE, de-AT	de
es, es-ES, es-MX	es

Chinese stays split by script (zh-CN / zh-TW) because Simplified and Traditional differ by script rather than by region.

Fallback chain

fallbackLng: { en: ["en-US"], zh: ["zh-CN"], ja: ["ja"], ko: ["ko"],
               fr: ["fr"], it: ["it"], de: ["de"], es: ["es"],
               default: ["en-US"] }

An untranslated locale (pt-BR, ru-RU, ...) still lands on English rather than Chinese.

Tests

28 -> 80 cases. Beyond the expanded resolution table, the bundles are checked structurally - every locale must:

• expose the same key set as en-US (catches a missing or leftover key)
• keep identical {{placeholders}} (a dropped one renders as a blank gap)
• leave no key empty
• leave browser-skill / BrowserSkill untranslated

OK packages/i18n  80/80
OK apps/extension 798/798
OK tsc --noEmit, biome check, pnpm ext:build all clean

Notes for reviewers

• Bundle size: 1.15 MB -> 1.24 MB (+90 KB, ~7.8%). All nine bundles are statically imported as decided. This is larger than the ~30 KB estimated during planning because the JSON is not tree-shaken per locale; switching to dynamic per-locale loading remains possible if this matters.
• Built on fix(i18n): match browser locale by language subtag instead of exact code #174: this branch stacks on the locale-normalisation work, so it contains that commit too, and can be rebased once fix(i18n): match browser locale by language subtag instead of exact code #174 merges.
• Translation notes: covers the 74 existing strings. Terms like daemon, protocol, instance ID and trace are kept consistent across languages. The stateBadge values (Standby / Igniting / Ready / Off) stay in English, matching the deliberate choice already made in the zh-CN bundle.

Closes #168