Fix service discovery to show all configured services regardless of state

Changed service discovery from 'systemctl list-units --all' to 'systemctl list-unit-files'
to ensure ALL service unit files are discovered, including services that have never been started.

Changes:
- Updated systemctl command to use list-unit-files instead of list-units --all
- Modified parsing logic to handle unit file format (2 fields vs 4 fields)
- Set placeholder values in discovery cache, actual runtime status fetched during collection
- This ensures all configured services (like inactive ARK servers) appear in dashboard

The issue was that list-units --all only shows services systemd has loaded/attempted to load,
but list-unit-files shows ALL service unit files regardless of their runtime state.

Cargo.lock

@@ -270,7 +270,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.29"
+version = "0.1.30"
 dependencies = [
  "anyhow",
  "chrono",
@@ -291,7 +291,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.29"
+version = "0.1.30"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -314,7 +314,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.29"
+version = "0.1.30"
 dependencies = [
  "chrono",
  "serde",