feat: use uber-go/zap for logging

[Vuks69]

https://github.com/uber-go/zap

Zap is extremely performant and widely used across the industry. It allows for extensive configuration and works well with both production- and dev-deployments with different output formats.

[whitespire]

#18 implements this

[Vuks69]

Agreement reached in Discord:

• slog should be good enough, zap is overkill for now
• to be revisited once speed/latency become an issue