Add health check endpoint and resolve locale detection bug (#387)

* Add health check API endpoint with database connectivity

* Update locale handling to fallback to default language on invalid input

* Add health check endpoints for application readiness and liveness

- Introduced `/api/health/readiness` endpoint to check if the application can serve requests, including database connectivity.
- Introduced `/api/health/liveness` endpoint to verify if the application is running independently of external dependencies.
- Updated the health check logic to streamline database connectivity checks and response handling.

* Refactor health check logic

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Co-authored-by: Julen Dixneuf <julen.d@padoa-group.com>

src/lib/locale.ts

@@ -17,7 +17,8 @@ function getAcceptLanguageLocale(requestHeaders: Headers, locales: Locales) {
   try {
     locale = match(languages, locales, defaultLocale)
   } catch (e) {
-    // invalid language
+    // invalid language - fallback to default
+    locale = defaultLocale
   }
   return locale
 }