Add Indonesian (id) locale + backfill missing hi/zh keys to full parity

[Zulfazli (fazelllyyy)]

Summary

Adds full Bahasa Indonesia (id) support for the frontend i18n system, following the same pattern as the Hindi locale in #436. While verifying, I found the hi and zh bundles had fallen behind en, so this PR also backfills those missing keys. Related to #337 (International Language Support).

Commits

1. Add Indonesian (id) locale for frontend i18n — the new locale
2. Backfill missing hi and zh locale keys to full parity with en — catch-up for existing locales

Changes

• New locale bundle src/i18n/locales/id/ — all 10 domains translated (common, upload, chart, model, encoding, messages, navigation, dataLoading, loader, errors) plus the index.ts aggregator
• Registered id in src/i18n/locales/index.ts and in the resources map in src/i18n/index.ts (it flows automatically into SUPPORTED_UI_LANGUAGES)
• Added the Bahasa Indonesia label to LANGUAGE_LABELS in src/app/App.tsx
• Extended tests/frontend/unit/app/i18nLocales.test.ts with an id-vs-en key-parity test
• hi: +36 keys (chartRec quick actions/report/workflow, dataThread source-switching + import counts, 12 sidebar keys incl. the semantic* set, 15 upload keys incl. connectorGroups, operation.virtualSource)
• zh: +5 keys (chartRec quick actions/report/workflow set, operation.virtualSource)

Translation notes

• Indonesian: formal Indonesian ("Anda"), KBBI-consistent terminology (e.g. Simpan, Batal, Muat, Segarkan, Bagan, Utas Data)
• Hindi backfill: follows the existing hi vocabulary (वर्कस्पेस, सिमेंटिक, वर्कफ़्लो, जोड़ें/नया/आयात करें); each key's meaning confirmed against its component usage (DataSourceSidebar.tsx, SimpleChartRecBox.tsx, SourceTableShelf.tsx, UnifiedDataUploadDialog.tsx, DataOperationCard.tsx)
• Chinese backfill: follows existing zh vocabulary (工作流, 语义/度量/维度, 快捷操作)
• Translation keys untouched; all {{interpolation}} placeholders, _plural forms, and inline HTML tags (<refreshAction>, <strong>) preserved verbatim
• Untranslatable identifiers kept in English per TRANSLATION_GUIDE.md (chart types, channel keys, spec values); tooltips translated instead
• Commands, code snippets, paths, and URLs in loader.json left literal
• chart.vegaLocale localized for Indonesian (day/month names); no code change needed in vega-locale.ts
• No backend change needed — "id" already exists in LANGUAGE_DISPLAY_NAMES (agent_language.py), so agent language instructions work out of the box

Verification

• JSON validity: all locale files parse cleanly
• Key parity across bundles (same spread-merge semantics as index.ts): en/hi/zh/id each resolve to exactly 1860 keys — 0 missing, 0 extra, 0 placeholder/tag mismatches
• New unit test asserts id key alignment with en
• Note: a full vitest/tsc run was not possible in this environment (no node_modules available); please rely on CI
  Base / head: base: microsoft/dev ← head: fazelllyyy/feat/locale-id

[Zulfazli (fazelllyyy)]

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