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/ai_serving/planner/passthrough/provider/family/candidates.rs

@@ -26,6 +26,7 @@ use crate::ai_serving::{
 };
 use crate::client_session_affinity::client_session_affinity_from_api_request;
 use crate::clock::current_unix_secs;
+use crate::scheduler::config::SchedulerOrderingConfig;
 use crate::{AppState, GatewayError};
 
 use super::{
@@ -140,6 +141,10 @@ pub(crate) async fn materialize_local_same_format_provider_candidate_attempts(
             current_unix_secs(),
             false,
             spec.operation.map(|operation| operation.as_str()),
+            input
+                .routing_policy
+                .as_ref()
+                .map(SchedulerOrderingConfig::from_routing_policy),
         )
         .await?;
     let outcome = materialize_local_execution_candidates_with_serving(
@@ -246,6 +251,10 @@ pub(crate) async fn build_local_same_format_provider_candidate_attempt_source<'a
             current_unix_secs(),
             false,
             spec.operation.map(|operation| operation.as_str()),
+            input
+                .routing_policy
+                .as_ref()
+                .map(SchedulerOrderingConfig::from_routing_policy),
         )
         .await?;