Cardano Updates

Adds `perSystem/packages/module-docs.nix` which builds
`nixosOptionsDoc`-based Markdown for all cardano-parts options:

  nix build .#module-docs-nixos   # NixOS module options
  nix build .#module-docs-flake   # flake module options
  nix build .#module-docs         # both combined

NixOS modules (Tier 1-3 fully documented):
- profile-cardano-node-topology, module-nginx-vhost-exporter,
  profile-aws-ec2-ephemeral, profile-cardano-postgres,
  profile-mithril-relay, profile-cardano-custom-metrics,
  profile-tcpdump, profile-blockperf, profile-grafana-alloy,
  profile-cardano-node-group, role-block-producer,
  profile-cardano-db-sync, profile-cardano-db-sync-snapshots,
  profile-cardano-webserver, profile-cardano-faucet,
  profile-cardano-metadata, profile-cardano-smash,
  service-cardano-faucet

Flake modules (all four namespaces documented):
- flake.cardano-parts.cluster, flake.cardano-parts.pkgs,
  flake.cardano-parts.lib, flake.cardano-parts.aws

Flake docs use a standalone lib.evalModules with only the four
cardano-parts flake modules rather than the full flake-parts
eval (which would trigger perSystem package evaluation without a
system context, causing a "process-compose option has no value"
error). All complex defaults in flakeModules get defaultText to
prevent stack overflow in generators.toPretty (the self-referential
groupFlake = flake default was the original trigger).

Supporting changes:
- flakeModules/cluster.nix: add defaultText to all complex defaults;
  allow null in optionCheck; fix conditional kms/bucketName defaults;
  fix groupMeta.domain type to nullOr str
- flakeModules/pkgs.nix: add defaultText to mkPkg helper and all
  special function options
- flakeModules/shell.nix: add defaultText to complex shell defaults
- flakeModules/aws.nix: add defaultText with literalExpression to
  rawSpec and spec options
- flake/nixosModules/profile-cardano-parts.nix: drop deprecated
  lib.mdDoc wrappers (plain strings are now implicit Markdown)

<!-- Describe your change here -->

Follow-up on #2486

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<!-- Consider each and tick it off one way or the other -->
* [X] CHANGELOG updated or not needed
* [X] Documentation updated or not needed
* [X] Haddocks updated or not needed
* [X] No new TODOs introduced or explained herafter

Signed-off-by: Chris Gianelloni <[email protected]>

Signed-off-by: Jonathan Lim <[email protected]>

* feat: bundle v1 and lace-extension

* feat: align UI with v2-bundle improvements

* feat: add v2 bundle feature flag

* chore: update v2 submodule to latest main