refactor: remove deployment.json and use direct selectors

- Remove deployment.json file generation from outputs.nix
- Add throw for deprecated deployment.file usage with upgrade instructions
- Remove vars data from deployment.data
- Update Machine class to use direct select() calls instead of deployment property
- Update all deployment property accesses to use direct selectors
- Add precaching for frequently accessed values in update.py:
  - Module paths for facts and vars
  - Deployment settings (requireExplicitUpdate, nixosMobileWorkaround)
  - Services and generators data
  - Secret upload locations
- This removes unnecessary JSON serialization and makes the code more composable

pkgs/generate-test-vars/generate_test_vars/cli.py

@@ -161,7 +161,6 @@ def main() -> None:
     flake.precache(
         [
             f"checks.{test_system}.{opts.check_attr}.machinesCross.{system}.{{{','.join(machine_names)}}}.config.clan.core.vars.generators.*.validationHash",
-            f"checks.{test_system}.{opts.check_attr}.machinesCross.{system}.{{{','.join(machine_names)}}}.config.system.clan.deployment.file",
         ]
     )