feat: implement RESP server

[chu-k]

Can now:

• Connect via redis-py and execute GET, i.e.

import redis
r = redis.Redis(host=..., port=...)

# existing key
r.get('foo')
# returns b'bar'

# no key
r.get('key')
# returns null

# unimplemented SET
r.set('key', 'value')
# rasies redis.exceptions.ResponseError: unimplemented command 'SET'

TODO:

• implement handling of other primitive types, currently all returned as bulk string
• configuration, docker compose service definition
• connect to actual cache + redis backing container for end-to-end testing