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)

* Bumps blockfrost-platform -> 0.0.3-rc3
* Bumps cardano-address -> 4.0.2
* Bumps cardano-signer -> v1.34.0
* Bumps isd -> v0.6.1
* Bumps ogmios -> v6.14.0
* Bumps process-compose -> v1.90.0