feat(enrichment): i18n hardcoded-string regression analyzer

[JSONbored]

New REES local analyzer (the i18n half of the #1499 epic 'accessibility and i18n regression' idea) that flags user-facing string literals newly added directly in JSX/UI code in a repo that otherwise uses a translation function (t('...') / i18n / FormattedMessage) — a localization regression. Detects the repo's i18n convention from the diff itself; pure compute, no network.

Deliverables

• Add I18nFinding ({ file, line }) + i18n? key to review-enrichment/src/types.ts (no string content returned)
• Create review-enrichment/src/analyzers/i18n-regression.ts: only activate when added lines in the PR also show an i18n call convention; then flag added JSX text nodes / user-facing string props that bypass it; skip when no i18n convention is present; cap with maxFindings
• Register a local descriptor (category 'quality', cost 'local', requires ['files']) with inline render() in review-enrichment/src/analyzers/registry.ts
• Add review-enrichment/test/i18n-regression.test.ts covering a hardcoded string flagged when i18n is in use, no findings when the repo shows no i18n convention, and the cap

References

• review-enrichment/src/analyzers/iac-misconfig.ts (local line-rule template)
• review-enrichment/src/analyzers/registry.ts:158-175
• gh issue 1499 lists 'Accessibility and i18n regression detector' (this bounty is the i18n half; the a11y half is a separate bounty)

Part of #1499.

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size: S · gittensor:feature

[linear-code]

JSO-2146