Implement per-service disk usage monitoring

Replaced system-wide disk usage with accurate per-service tracking by scanning
service-specific directories. Services like sshd now correctly show minimal
disk usage instead of misleading system totals.

- Rename storage widget and add drive capacity/usage columns
- Move host display to main dashboard title for cleaner layout
- Replace separate alert displays with color-coded row highlighting
- Add per-service disk usage collection using du command
- Update services widget formatting to handle small disk values
- Restructure into workspace with dedicated agent and dashboard packages

agent/Cargo.toml

@@ -6,13 +6,18 @@ edition = "2021"
 [dependencies]
 cm-dashboard-shared = { path = "../shared" }
 anyhow = "1.0"
+async-trait = "0.1"
 clap = { version = "4.0", features = ["derive"] }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 chrono = { version = "0.4", features = ["serde"] }
+thiserror = "1.0"
+toml = "0.8"
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["fmt", "env-filter"] }
 tracing-appender = "0.2"
 zmq = "0.10"
-tokio = { version = "1.0", features = ["full"] }
+tokio = { version = "1.0", features = ["full", "process"] }
+futures = "0.3"
 rand = "0.8"
+gethostname = "0.4"