Composition Root in main() and wiring.

[JoTurk]

Create a single composition root that constructs and wires all components with constructor injection.

I think we have some options.

1. Manual DI

• Pros: Explicit; No magic
• Cons: Verbose, harder to test

2. Google Wire

• Pros: Compile-time checks
• Cons: Codegen step, we'll have to add a build setup and script, using justfile or something, Wire is no longer maintained so we'll have to fork it.

3. Uber Fx

• Pros: Lifecycle hooks
• Cons: Reflection/magic, slower
  (we're open to any other option)

tasks

• Return cleanup functions from constructors. aggregate and defer
• App starts with explicit wiring. no hidden globals
• Global context manager and graceful startup and shutdown with timeouts for modules.
• go test can construct core with fakes