fix: add missing tier field to all AppMetadata, fix build errors

- Add tier: "" to all AppMetadata match arms (was missing from 30+ arms)
- Use std::thread::available_parallelism() instead of num_cpus crate
- Remove unused num_cpus dependency
- Fix unused variable warning in health_monitor.rs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/archipelago/Cargo.toml

@@ -83,8 +83,6 @@ zeroize = { version = "1.7", features = ["derive"] }
 # Systemd watchdog notification
 sd-notify = "0.4"
 
-# CPU core count detection
-num_cpus = "1.16"
 
 [dev-dependencies]
 tokio-test = "0.4"