refactor(beszel): switch to universal token via secrets/common.yaml

Replace per-host host-token.nix imports with a single beszel-token secret
in secrets/common.yaml, wired once in enable-agent.nix. Host files now only
need services.beszel.agent.environment.KEY — no imports block required.

Delete modules/beszel/host-token.nix (no longer referenced anywhere).

Action needed: run `sops secrets/common.yaml` and add `beszel-token: <value>`
from the beszel hub UI before deploying.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/beszel/enable-agent.nix

@@ -1,10 +1,22 @@
-{ vars, ... }:
+{ config, vars, ... }:
 
 {
-  services.beszel.agent.enable = true;
-  services.beszel.agent.environment = {
-    #DOCKER_HOST = "tcp://docker-socket-proxy:2375";
-    HUB_URL = "http://${vars.dockerHost}.${vars.homeDomain}:${toString vars.ports.beszelHub}";
+  # Universal token shared by all beszel agents. Add to secrets/common.yaml:
+  #   sops secrets/common.yaml
+  #   beszel-token: <value from the beszel hub UI>
+  sops.secrets."beszel-token" = { };
+
+  sops.templates."beszel.env".content = ''
+    TOKEN=${config.sops.placeholder."beszel-token"}
+  '';
+
+  services.beszel.agent = {
+    enable = true;
+    environmentFile = config.sops.templates."beszel.env".path;
+    environment = {
+      #DOCKER_HOST = "tcp://docker-socket-proxy:2375";
+      HUB_URL = "http://${vars.dockerHost}.${vars.homeDomain}:${toString vars.ports.beszelHub}";
+    };
   };
 
   # The upstream module runs beszel-agent under DynamicUser with

modules/beszel/host-token.nix

@@ -1,11 +0,0 @@
-{ name, sopsFile }:
-
-{ config, ... }:
-
-{
-  sops.secrets."beszel-token".sopsFile = sopsFile;
-  sops.templates."${name}-beszel.env".content = ''
-    TOKEN=${config.sops.placeholder."beszel-token"}
-  '';
-  services.beszel.agent.environmentFile = config.sops.templates."${name}-beszel.env".path;
-}