ci(frontend): validate translation keys

[TNT-Likely]

Background

Missing i18n resource paths currently fall back to rendering the raw key. The existing check only detects untranslated literals, so incorrect namespace paths and scoped dynamic prefixes can reach users.

Changes

• Extend the TypeScript AST check to resolve translation namespaces, aliases, scoped wrappers, static keys, and dynamic key prefixes against both locale catalogs.
• Add positive and negative fixtures covering the two failure modes found in the recent translation audit.
• Add a lightweight pull-request workflow limited to relevant TypeScript and translation changes; it uses pnpm caching and runs only the i18n check.

Validation

• pnpm check:i18n — passed for 105 migrated files.
• pnpm exec vitest run — 30 files and 84 tests passed.
• pnpm build — passed.
• .venv/bin/python -m pytest tests/ -x -q — 808 passed, 3 skipped.
• .venv/bin/python -m pytest packages/marketdata/tests -q — 188 passed.
• git diff --check — passed.

Boundaries and risks

• Fully runtime-generated keys without a static prefix remain outside static validation.
• The workflow runs only for pull requests touching relevant TypeScript, resource, checker, or fixture files.

Follow-up

• None.