Complete systemd collector restoration matching original architecture

- Add nginx site metrics caching with configurable intervals matching original
- Implement complex nginx config parsing with brace counting and redirect detection
- Replace curl with reqwest HTTP client for proper timeout and redirect handling
- Fix docker container parsing to use comma format with proper status mapping
- Add sudo to directory size command for permission handling
- Change nginx URLs to use https protocol matching original
- Add advanced NixOS ExecStart parsing for argv[] format support
- Add nginx -T fallback functionality for config discovery
- Implement proper server block parsing with domain validation and brace tracking
- Add get_service_memory function matching original signature

All functionality now matches pre-refactor implementation architecture.

Cargo.lock

@@ -279,7 +279,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.142"
+version = "0.1.144"
 dependencies = [
  "anyhow",
  "chrono",
@@ -301,7 +301,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.142"
+version = "0.1.144"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -324,7 +324,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.142"
+version = "0.1.144"
 dependencies = [
  "chrono",
  "serde",