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/router/properties.nix

@@ -0,0 +1,21 @@
+{
+  hostNames = [
+    "router"
+    "192.168.1.228"
+  ];
+
+  arch = "x86_64-linux";
+
+  systemRoles = [
+    "server"
+    "wireless"
+    "router"
+  ];
+
+  hostKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFr2IHmWFlaLaLp5dGoSmFEYKA/eg2SwGXAogaOmLsHL";
+
+  remoteUnlock = {
+    hostKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJOw5dTPmtKqiPBH6VKyz5MYBubn8leAh5Eaw7s/O85c";
+    onionHost = "jxx2exuihlls2t6ncs7rvrjh2dssubjmjtclwr2ysvxtr4t7jv55xmqd.onion";
+  };
+}