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/src/health_monitor.rs

@@ -368,7 +368,6 @@ pub fn spawn_health_monitor(state: Arc<StateManager>, data_dir: PathBuf) {
             let mut prev_tier: Option<StartupTier> = None;
             for container in &unhealthy {
                 let tier = container_tier(&container.name);
-                let attempts = tracker.attempt_count(&container.name);
 
                 // Reset counter after 1 hour for permanently failed containers
                 if tracker.should_reset_failed(&container.name) {