Feature: Support internationalization

[giorgiodg]

Context:

• next-intl library was introduced to handle i18n
• The chosen approach was App Router setup without i18n routing because it doesn't require to change the URL structure to support prefixes (e.g. /en/about)

New files added:

• messages/en.json
• messages/it.json (partially translated)

Caveats:

• right now the locale is hardcoded, the logic to handle it dinamiycally must be designed and implemented
• messages/it.json is partially translated