fix(colmena): expose colmenaHive for the nix-community evaluator (#361)

* fix(colmena): expose colmenaHive for the new evaluator

nixpkgs now ships the nix-community Colmena rewrite, whose default
evaluator reads an evaluated colmenaHive flake output instead of the raw
colmena hive. Without it every colmena apply recipe failed with
"does not provide attribute colmenaHive".

Add a colmena input pinned to the same v0.5.0 as nixpkgs and expose
colmenaHive = colmena.lib.makeHive <raw hive>, with the raw hive kept as
an internal binding rather than a flake output of its own.

* chore: clean up stale colmena and aquamarine references

- point the Colmena links at nix-community/colmena after the move
- rename the security-aquamarine-metrics test to youko-metrics (it
  already tested youko) and update the outputs README
- drop the commented aquamarine remote-builder example

README.md

@@ -146,8 +146,8 @@ just local
 just local debug  # detailed output (macOS has no switch/boot mode)
 ```
 
-Remote / cluster hosts are deployed with [Colmena](https://github.com/zhaofengli/colmena) on top of
-the same flake, e.g. `just col <tag>`, `just k3s-test`, `just lab`.
+Remote / cluster hosts are deployed with [Colmena](https://github.com/nix-community/colmena) on top
+of the same flake, e.g. `just col <tag>`, `just k3s-test`, `just lab`.
 
 > [What y'all will need when Nix drives you to drink.](https://www.youtube.com/watch?v=Eni9PPPPBpg)
 > (copy from hlissner's dotfiles, it really matches my feelings when I first started using NixOS...)