Refactor imports and secrets. Add per system properties and role based secret access.

Highlights
- No need to update flake for every machine anymore, just add a properties.nix file.
- Roles are automatically generated from all machine configurations.
- Roles and their secrets automatically are grouped and show up in agenix secrets.nix
- Machines and their service configs may now query the properties of all machines.
- Machine configuration and secrets are now competely isolated into each machine's directory.
- Safety checks to ensure no mixing of luks unlocking secrets and hosts with primary ones.
- SSH pubkeys no longer centrally stored but instead per machine where the private key lies for better cleanup.

machines/phil/properties.nix

@@ -0,0 +1,19 @@
+{
+  hostNames = [
+    "phil"
+    "phil.neet.dev"
+  ];
+
+  arch = "aarch64-linux";
+
+  systemRoles = [
+    "server"
+  ];
+
+  hostKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIBlOs6mTZCSJL/XM6NysHN0ZNQAyj2GEwBV2Ze6NxRmr";
+
+  remoteUnlock = {
+    hostKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIAqy9X/m67oXJBX+OMdIqpiLONYc5aQ2nHeEPAaj/vgN";
+    clearnetHost = "unlock.phil.neet.dev";
+  };
+}