Add service metrics from systemctl (memory, uptime, restarts)

Shared:
- Add memory_bytes, restart_count, uptime_seconds to ServiceData

Agent:
- Add new fields to ServiceStatusInfo struct
- Fetch MemoryCurrent, NRestarts, ExecMainStartTimestamp from systemctl show
- Calculate uptime from start timestamp
- Parse and populate new fields in ServiceData
- Remove unused load_state and sub_state fields

Dashboard:
- Add memory_bytes, restart_count, uptime_seconds to ServiceInfo
- Update header: Service, Status, RAM, Uptime, ↻ (restarts)
- Format memory as MB/GB
- Format uptime as Xd Xh, Xh Xm, or Xm
- Show restart count with ! prefix if > 0 to indicate instability

All metrics obtained from single systemctl show call - zero overhead.

Cargo.lock

@@ -279,7 +279,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.204"
+version = "0.1.205"
 dependencies = [
  "anyhow",
  "chrono",
@@ -301,7 +301,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.204"
+version = "0.1.205"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -324,7 +324,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.204"
+version = "0.1.205"
 dependencies = [
  "chrono",
  "serde",