feat: ssl context management

[braindigitalis]

Instead of creating a new ssl context for every connection, we only need:

• one SSL context for all client connections
• one for each listening port, with the SSL private key and public key loaded into it

This saves on memory of having to keep copies of the context around, and also massively cuts down on cpu use. Creating an SSL context from scratch means loading the cert store and root certs, generating things, loading private and public keys from disk and more.

Code change checklist

• I have ensured that all methods and functions are fully documented using doxygen style comments.
• My code follows the coding style guide.
• I tested that my change works before raising the PR.
• I have ensured that I did not break any existing API calls.
• I have not built my pull request using AI, a static analysis tool or similar without any human oversight.

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[RealTimeChris]

Looks good to me. Nicely done.

[Neko-Life]

lgtm