feat(routing): make routing profiles the sole scheduler policy source

Bootstrap an enabled system-default routing group from the legacy
scheduler config keys on startup, resolve the default ordering config
from that group before falling back to the legacy keys, and stop merging
keep_priority_on_conversion with the legacy flag when a policy is
resolved. Thread the policy-derived ordering config into candidate
preselection so it no longer reads system config independently.

Add per-API-format key priority overrides so a key serving several
formats keeps independent ordering, matching the legacy
global_priority_by_format semantics. Expose keep_priority_on_conversion
in the routing profile editor and read the effective policy in the
model routing preview, monitoring metrics and provider page badge.

apps/aether-gateway/src/scheduler/candidate/tests/required_capability.rs

@@ -65,6 +65,7 @@ async fn compatible_required_capability_prefers_matching_keys_without_hard_filte
         None,
         None,
         100,
+        None,
     )
     .await
     .expect("selection should succeed");
@@ -120,6 +121,7 @@ async fn exclusive_required_capability_keeps_hard_filtering_only_matching_keys()
         None,
         None,
         100,
+        None,
     )
     .await
     .expect("selection should succeed");
@@ -196,6 +198,7 @@ async fn required_capability_without_model_uses_session_scoped_affinity() {
         Some(&auth_snapshot),
         Some(&client_session_affinity),
         100,
+        None,
     )
     .await
     .expect("selection should succeed");
@@ -273,6 +276,7 @@ async fn required_capability_reports_auth_limit_signal_when_every_model_is_block
             Some(&auth_snapshot),
             None,
             100,
+            None,
         )
         .await
         .expect("selection should succeed");

apps/aether-gateway/src/scheduler/candidate/tests/selection.rs

@@ -75,6 +75,7 @@ async fn collect_selectable_candidates(
         None,
         now_unix_secs,
         false,
+        None,
     )
     .await
 }