fix(i18n,email): request-aware validation i18n, bounce suppression, C…

[fadee26]

Summary

Closes #1237
Closes #1234
Closes #1233
Closes #1232

#1237 – I18nService failure/fallback coverage

• Specs for malformed JSON → empty catalogue + warn, missing files, dual-load failure.
• RFC 7231 edges: empty header, q=0, wildcard *, equal-q ordering.
• Interpolation with missing params; nested lookup through arrays/non-objects.
• Parser now skips q=0 and pure * tags.

#1234 – ValidationPipe uses request language

• Added src/common/request-language.store.ts (AsyncLocalStorage).
• Middleware in main.ts stores Accept-Language / x-language / user.languagePreference.
• exceptionFactory reads the store and passes acceptLanguageHeader + userPreference into i18n.translate (no longer hard-coded undefined).

#1233 – Bounce-aware send suppression

• shouldSuppressAddress() counts recent HARD bounces and COMPLAINED events (90-day window, threshold 1).
• sendEmail skips queueing when suppressed; also skips emailStatus === 'BOUNCED'.
• Specs cover suppress / allow paths.

#1232 – Unsubscribe URL from ConfigService

• Removed module-level const UNSUBSCRIBE_URL = process.env.FRONTEND_URL ….
• buildListUnsubscribeHeader reads FRONTEND_URL via ConfigService at call time and uses buildUnsubscribeUrl.
• Specs assert different config values produce different List-Unsubscribe headers.

Test plan

npm test -- --testPathPattern='i18n.service|email.service'
# optional e2e: request with Accept-Language: es should return Spanish validation messages

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[nanaf6203-bit]

@fadee26 please resolve conflicts