Static metadata in [lang] route should be made dynamic

As discussed in [PR #422](https://github.com/bitcashorg/smartsale/pull/422), the whitepaper page currently uses static metadata in a [lang] route. This should be improved by converting static metadata to dynamic using `generateMetadata` with translations from the dictionary.

See the PR comment: https://github.com/bitcashorg/smartsale/pull/422#discussion_r1859815444

Requested by @AndlerRL.