refactor: replace legacy Config with Settings

Remove legacy src/config.rs and migrate all application consumers to
the nested Settings model. Baseliner, metrics, pingers, ratecontroller,
reflector selector, and main now use Settings. Derived min rates become
methods on NetworkSettings rather than stored legacy fields.
MeasurementType and ObservabilityProtocol move into the settings module.

src/reflector_selector.rs

@@ -5,10 +5,10 @@
 //
 // SPDX-License-Identifier: MPL-2.0
 
-use crate::Config;
 use crate::SHUTDOWN;
 use crate::baseliner::ControlSnapshot;
 use crate::metrics::{Metric, MetricsSender};
+use crate::settings::Settings;
 use crate::util::RwLockExt;
 use flume::{Receiver, RecvError, RecvTimeoutError, Selector};
 use log::{debug, info};
@@ -105,7 +105,7 @@ fn recent_rtt_for_peer(snapshot: Option<&ControlSnapshot>, peer: &IpAddr) -> Opt
 }
 
 pub struct ReflectorSelector {
-    pub config: Config,
+    pub settings: Settings,
     pub snapshot_rx: Receiver<ControlSnapshot>,
     pub reflector_peers_lock: Arc<RwLock<Vec<IpAddr>>>,
     pub reflector_pool: Vec<IpAddr>,
@@ -118,8 +118,9 @@ impl ReflectorSelector {
         let mut selector_sleep_time = Duration::new(30, 0);
         let mut reselection_count = 0;
         let mut latest_snapshot = None;
-        let baseline_sleep_time =
-            Duration::from_secs_f64(self.config.tick_interval * std::f64::consts::PI);
+        let baseline_sleep_time = Duration::from_secs_f64(
+            self.settings.advanced_settings.tick_interval * std::f64::consts::PI,
+        );
         // Initial wait of several seconds to allow some OWD data to build up
         receive_snapshots_until(
             &self.snapshot_rx,
@@ -157,7 +158,10 @@ impl ReflectorSelector {
 
             // After 40 reselections, slow down to every 15 minutes
             if reselection_count > 40 {
-                selector_sleep_time = Duration::new(self.config.peer_reselection_time * 60, 0);
+                selector_sleep_time = Duration::new(
+                    self.settings.advanced_settings.peer_reselection_time * 60,
+                    0,
+                );
             }
 
             let mut next_peers: Vec<IpAddr> = Vec::new();
@@ -216,7 +220,7 @@ impl ReflectorSelector {
             candidates.sort_by(|a, b| a.1.cmp(&b.1));
 
             // Now we will just limit the candidates down to 2 * num_reflectors
-            let mut num_reflectors = self.config.num_reflectors;
+            let mut num_reflectors = self.settings.advanced_settings.num_reflectors;
             let candidate_pool_num = (2 * num_reflectors) as usize;
             candidates.truncate(candidate_pool_num);