refactor: 拆分 gateway 单体为独立 crate，新增 systemd 部署方案

将 gateway 内部的 model-fetch、provider-transport、scheduler-core、
usage-runtime、video-tasks-core 模块提取为独立 crate；重构 gateway
内部模块结构（state/router/cache/data/query 等）；移除大量遗留模块
文件；新增 systemd 二进制部署骨架及相关文档；更新前端 usage 相关
API 和组件。

apps/aether-gateway/src/scheduler/candidate/affinity.rs

@@ -1,16 +1,17 @@
-use sha2::{Digest, Sha256};
+pub(super) use aether_scheduler_core::{
+    build_scheduler_affinity_cache_key_for_api_key_id, candidate_affinity_hash, candidate_key,
+    compare_affinity_order, matches_affinity_target, SchedulerAffinityTarget,
+};
 
-use crate::gateway::gateway_cache::SchedulerAffinityTarget;
-use crate::gateway::gateway_data::StoredGatewayAuthApiKeySnapshot;
-use crate::gateway::AppState;
+use crate::data::auth::GatewayAuthApiKeySnapshot;
 
 use super::{
-    normalize_api_format, GatewayMinimalCandidateSelectionCandidate,
+    GatewayMinimalCandidateSelectionCandidate, SchedulerRuntimeState,
     SCHEDULER_AFFINITY_MAX_ENTRIES, SCHEDULER_AFFINITY_TTL,
 };
 
 pub(super) fn build_scheduler_affinity_cache_key(
-    auth_snapshot: Option<&StoredGatewayAuthApiKeySnapshot>,
+    auth_snapshot: Option<&GatewayAuthApiKeySnapshot>,
     api_format: &str,
     global_model_name: &str,
 ) -> Option<String> {
@@ -20,87 +21,18 @@ pub(super) fn build_scheduler_affinity_cache_key(
     build_scheduler_affinity_cache_key_for_api_key_id(api_key_id, api_format, global_model_name)
 }
 
-pub(super) fn build_scheduler_affinity_cache_key_for_api_key_id(
-    api_key_id: &str,
-    api_format: &str,
-    global_model_name: &str,
-) -> Option<String> {
-    let api_key_id = api_key_id.trim();
-    if api_key_id.is_empty() {
-        return None;
-    }
-    let api_format = normalize_api_format(api_format);
-    let global_model_name = global_model_name.trim();
-    if api_format.is_empty() || global_model_name.is_empty() {
-        return None;
-    }
-
-    Some(format!(
-        "scheduler_affinity:{api_key_id}:{api_format}:{global_model_name}"
-    ))
-}
-
-pub(super) fn compare_affinity_order(
-    left: &GatewayMinimalCandidateSelectionCandidate,
-    right: &GatewayMinimalCandidateSelectionCandidate,
-    affinity_key: Option<&str>,
-) -> std::cmp::Ordering {
-    let Some(affinity_key) = affinity_key else {
-        return std::cmp::Ordering::Equal;
-    };
-
-    candidate_affinity_hash(affinity_key, left).cmp(&candidate_affinity_hash(affinity_key, right))
-}
-
-pub(super) fn candidate_affinity_hash(
-    affinity_key: &str,
-    candidate: &GatewayMinimalCandidateSelectionCandidate,
-) -> u64 {
-    let mut hasher = Sha256::new();
-    hasher.update(affinity_key.as_bytes());
-    hasher.update(b":");
-    hasher.update(candidate.provider_id.as_bytes());
-    hasher.update(b":");
-    hasher.update(candidate.endpoint_id.as_bytes());
-    hasher.update(b":");
-    hasher.update(candidate.key_id.as_bytes());
-    let digest = hasher.finalize();
-    u64::from_be_bytes([
-        digest[0], digest[1], digest[2], digest[3], digest[4], digest[5], digest[6], digest[7],
-    ])
-}
-
-pub(super) fn matches_affinity_target(
-    candidate: &GatewayMinimalCandidateSelectionCandidate,
-    target: &SchedulerAffinityTarget,
-) -> bool {
-    candidate.provider_id == target.provider_id
-        && candidate.endpoint_id == target.endpoint_id
-        && candidate.key_id == target.key_id
-}
-
-pub(super) fn candidate_key(
-    candidate: &GatewayMinimalCandidateSelectionCandidate,
-) -> (String, String, String) {
-    (
-        candidate.provider_id.clone(),
-        candidate.endpoint_id.clone(),
-        candidate.key_id.clone(),
-    )
-}
-
 #[cfg_attr(not(test), allow(dead_code))]
 pub(super) fn remember_scheduler_affinity(
     affinity_cache_key: Option<&str>,
-    state: &AppState,
+    state: &(impl SchedulerRuntimeState + ?Sized),
     candidate: &GatewayMinimalCandidateSelectionCandidate,
 ) {
     let Some(cache_key) = affinity_cache_key else {
         return;
     };
 
-    state.scheduler_affinity_cache.insert(
-        cache_key.to_string(),
+    state.remember_scheduler_affinity_target(
+        cache_key,
         SchedulerAffinityTarget {
             provider_id: candidate.provider_id.clone(),
             endpoint_id: candidate.endpoint_id.clone(),