refactor: 大规模模块拆分与代码精简，新增 ai-pipeline/data-contracts 独立 crate

- 新增 aether-ai-pipeline 和 aether-data-contracts crate，将 pipeline 逻辑与数据契约从 gateway 中解耦
- 重构 admin handlers：拆分单体模块为 auth/billing/endpoint/features/model/observability/provider/system 等独立子模块
- 合并 chat/cli 重复代码路径：精简 conversion、finalize、planner 中的 sync/chat/cli 分支
- 重构 scheduler/executor/data 层，引入 facade 模式降低模块间耦合
- 移除冗余的 intent 模块，将 plan_fallback/policy/stream_path/sync_path 迁移至 executor
- 前端适配：调整 admin API 调用和 provider 模型测试对话框

apps/aether-gateway/src/handlers/admin/model/shared/mod.rs

@@ -0,0 +1,5 @@
+mod paths;
+mod payloads;
+
+pub(crate) use self::paths::*;
+pub(crate) use self::payloads::*;

apps/aether-gateway/src/handlers/admin/model/shared/paths.rs

@@ -0,0 +1,46 @@
+pub(crate) fn is_admin_global_models_root(request_path: &str) -> bool {
+    matches!(
+        request_path,
+        "/api/admin/models/global" | "/api/admin/models/global/"
+    )
+}
+
+pub(crate) fn admin_global_model_id_from_path(request_path: &str) -> Option<String> {
+    let raw = request_path.strip_prefix("/api/admin/models/global/")?;
+    let normalized = raw.trim().trim_matches('/');
+    if normalized.is_empty()
+        || normalized.contains('/')
+        || normalized == "batch-delete"
+        || normalized.ends_with("/providers")
+        || normalized.ends_with("/assign-to-providers")
+        || normalized.ends_with("/routing")
+    {
+        None
+    } else {
+        Some(normalized.to_string())
+    }
+}
+
+pub(crate) fn admin_global_model_assign_to_providers_id(request_path: &str) -> Option<String> {
+    request_path
+        .strip_prefix("/api/admin/models/global/")?
+        .strip_suffix("/assign-to-providers")
+        .map(|value| value.trim().trim_matches('/').to_string())
+        .filter(|value| !value.is_empty() && !value.contains('/'))
+}
+
+pub(crate) fn admin_global_model_routing_id(request_path: &str) -> Option<String> {
+    request_path
+        .strip_prefix("/api/admin/models/global/")?
+        .strip_suffix("/routing")
+        .map(|value| value.trim().trim_matches('/').to_string())
+        .filter(|value| !value.is_empty() && !value.contains('/'))
+}
+
+pub(crate) fn admin_global_model_providers_id(request_path: &str) -> Option<String> {
+    request_path
+        .strip_prefix("/api/admin/models/global/")?
+        .strip_suffix("/providers")
+        .map(|value| value.trim().trim_matches('/').to_string())
+        .filter(|value| !value.is_empty() && !value.contains('/'))
+}

apps/aether-gateway/src/handlers/admin/model/shared/payloads.rs

@@ -0,0 +1,45 @@
+use serde::Deserialize;
+
+#[derive(Debug, Deserialize)]
+pub(crate) struct AdminGlobalModelCreateRequest {
+    pub(crate) name: String,
+    pub(crate) display_name: String,
+    #[serde(default)]
+    pub(crate) default_price_per_request: Option<f64>,
+    #[serde(default)]
+    pub(crate) default_tiered_pricing: Option<serde_json::Value>,
+    #[serde(default)]
+    pub(crate) supported_capabilities: Option<Vec<String>>,
+    #[serde(default)]
+    pub(crate) config: Option<serde_json::Value>,
+    #[serde(default)]
+    pub(crate) is_active: Option<bool>,
+}
+
+#[derive(Debug, Deserialize)]
+pub(crate) struct AdminGlobalModelUpdateRequest {
+    #[serde(default)]
+    pub(crate) display_name: Option<String>,
+    #[serde(default)]
+    pub(crate) is_active: Option<bool>,
+    #[serde(default)]
+    pub(crate) default_price_per_request: Option<f64>,
+    #[serde(default)]
+    pub(crate) default_tiered_pricing: Option<serde_json::Value>,
+    #[serde(default)]
+    pub(crate) supported_capabilities: Option<Vec<String>>,
+    #[serde(default)]
+    pub(crate) config: Option<serde_json::Value>,
+}
+
+#[derive(Debug, Deserialize)]
+pub(crate) struct AdminBatchDeleteIdsRequest {
+    pub(crate) ids: Vec<String>,
+}
+
+#[derive(Debug, Deserialize)]
+pub(crate) struct AdminBatchAssignToProvidersRequest {
+    pub(crate) provider_ids: Vec<String>,
+    #[serde(default)]
+    pub(crate) create_models: Option<bool>,
+}