refactor: reorganize server modules

- Moved each individual service definition into a dedicated `services/`
  directory under every server module (e.g.
`modules/servers/bragi/services/`).
- Updated the corresponding `default.nix` files to import the renamed
  service modules from the new location.
- Applied the same changes across all server modules, ensuring
  the API and import paths remain consistent.

modules/servers/thor/default.nix

@@ -1,10 +1,15 @@
-{...}: {
-  imports = [
-    ./changedetection-io.nix
-    ./forgejo.nix
-    ./secrets.nix
-    ./plausible.nix
-    ./conduit.nix
-    ./lemmy.nix
-  ];
+{...}: let
+  servicesDir = ./services;
+  serviceFiles =
+    builtins.filter
+    (name: builtins.match "^.*\\.nix$" name != null)
+    (builtins.attrNames (builtins.readDir servicesDir));
+  hostModules = map (fn: import "${servicesDir}/${fn}") serviceFiles;
+in {
+  imports =
+    [
+      ../general
+      ./secrets.nix
+    ]
+    ++ hostModules;
 }