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/mod.rs

@@ -1,149 +1,5 @@
-use std::collections::{BTreeMap, BTreeSet};
-use std::fs;
-use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
-
-use aether_contracts::{ExecutionPlan, ExecutionResult, ExecutionTimeouts, RequestBody};
-#[cfg(test)]
-use aether_crypto::DEVELOPMENT_ENCRYPTION_KEY;
-use aether_crypto::{decrypt_python_fernet_ciphertext, encrypt_python_fernet_plaintext};
-use aether_data::redis::{RedisKeyspace, RedisKvRunner};
-use aether_data::repository::candidate_selection::StoredMinimalCandidateSelectionRow;
-use aether_data::repository::candidates::{
-    PublicHealthTimelineBucket, RequestCandidateStatus, StoredRequestCandidate,
-};
-use aether_data::repository::global_models::{
-    AdminGlobalModelListQuery, AdminProviderModelListQuery, CreateAdminGlobalModelRecord,
-    PublicGlobalModelQuery, StoredAdminGlobalModel, StoredAdminProviderModel,
-    StoredPublicGlobalModel, UpdateAdminGlobalModelRecord, UpsertAdminProviderModelRecord,
-};
-use aether_data::repository::management_tokens::{
-    CreateManagementTokenRecord, ManagementTokenListQuery, RegenerateManagementTokenSecret,
-    StoredManagementToken, StoredManagementTokenUserSummary, UpdateManagementTokenRecord,
-};
-use aether_data::repository::oauth_providers::{
-    EncryptedSecretUpdate, UpsertOAuthProviderConfigRecord,
-};
-use aether_data::repository::provider_catalog::{
-    StoredProviderCatalogEndpoint, StoredProviderCatalogKey, StoredProviderCatalogProvider,
-};
-use aether_data::repository::proxy_nodes::{
-    ProxyNodeHeartbeatMutation, ProxyNodeTunnelStatusMutation, StoredProxyNode,
-    StoredProxyNodeEvent,
-};
-use aether_runtime::{maybe_hold_axum_response_permit, AdmissionPermit};
-use axum::body::{to_bytes, Body, Bytes};
-use axum::extract::{ConnectInfo, Request, State};
-use axum::http::header::{HeaderName, HeaderValue};
-use axum::http::Response;
-use axum::response::IntoResponse;
-use axum::Json;
-use base64::engine::general_purpose::URL_SAFE_NO_PAD;
-use base64::Engine as _;
-use chrono::{Datelike, SecondsFormat, Utc};
-use futures_util::TryStreamExt;
-use regex::Regex;
-pub(crate) use serde::Deserialize;
-pub(crate) use serde_json::{json, Value};
-use sha2::{Digest, Sha256};
-use tracing::info;
-pub(crate) use tracing::warn;
-use url::form_urlencoded;
-use url::Url;
-use uuid::Uuid;
-
-use crate::ai_pipeline::finalize::maybe_build_sync_finalize_outcome;
-use crate::ai_pipeline::planner::{
-    maybe_build_stream_decision_payload, maybe_build_stream_plan_payload,
-    maybe_build_sync_decision_payload, maybe_build_sync_plan_payload,
-};
-use crate::api::ai::{
-    admin_default_body_rules_for_signature, admin_endpoint_signature_parts,
-    public_api_format_local_path,
-};
-use crate::api::response::{
-    build_client_response, build_local_auth_rejection_response, build_local_http_error_response,
-    build_local_overloaded_response, build_local_user_rpm_limited_response,
-};
-use crate::audit::record_shadow_result_non_blocking;
-use crate::constants::*;
-use crate::control::{
-    allows_control_execute_emergency, maybe_execute_via_control, request_model_local_rejection,
-    resolve_public_request_context, should_buffer_request_for_local_auth,
-    trusted_auth_local_rejection, GatewayControlDecision, GatewayPublicRequestContext,
-};
-use crate::execution_runtime::{
-    execute_execution_runtime_stream, execute_execution_runtime_sync,
-    maybe_execute_via_execution_runtime_stream, maybe_execute_via_execution_runtime_sync,
-};
-use crate::fallback_metrics::{GatewayFallbackMetricKind, GatewayFallbackReason};
-use crate::headers::{
-    extract_or_generate_trace_id, header_value_str, should_skip_request_header,
-};
-use crate::provider_transport::provider_types::{
-    fixed_provider_template, provider_type_enables_format_conversion_by_default,
-    provider_type_is_fixed,
-};
-use crate::rate_limit::FrontdoorUserRpmOutcome;
-use crate::scheduler::{
-    count_recent_rpm_requests_for_provider_key_since, is_provider_key_circuit_open,
-    provider_key_health_score,
-};
-use crate::state::{AppState, LocalProviderDeleteTaskState};
-use crate::GatewayError;
-
-const ADMIN_PROVIDER_MAPPING_PREVIEW_MAX_KEYS: usize = 200;
-const ADMIN_PROVIDER_MAPPING_PREVIEW_MAX_MODELS: usize = 500;
-const ADMIN_PROVIDER_MAPPING_PREVIEW_FETCH_LIMIT: usize = 10_000;
-const ADMIN_PROVIDER_POOL_SCAN_BATCH: u64 = 200;
-const ADMIN_EXTERNAL_MODELS_CACHE_KEY: &str = "aether:external:models_dev";
-const ADMIN_EXTERNAL_MODELS_CACHE_TTL_SECS: u64 = 15 * 60;
-const ADMIN_PROVIDER_OAUTH_DATA_UNAVAILABLE_DETAIL: &str = "Admin provider OAuth data unavailable";
-
 pub(crate) mod admin;
 pub(crate) mod internal;
 pub(crate) mod proxy;
 pub(crate) mod public;
 pub(crate) mod shared;
-
-pub(crate) use admin::stats::{
-    admin_stats_bad_request_response, list_usage_for_optional_range, parse_bounded_u32, round_to,
-    AdminStatsTimeRange, AdminStatsUsageFilter,
-};
-pub(crate) use shared::*;
-
-pub(crate) const OFFICIAL_EXTERNAL_MODEL_PROVIDERS: &[&str] = &[
-    "anthropic",
-    "openai",
-    "google",
-    "google-vertex",
-    "azure",
-    "amazon-bedrock",
-    "xai",
-    "meta",
-    "deepseek",
-    "mistral",
-    "cohere",
-    "zhipuai",
-    "alibaba",
-    "minimax",
-    "moonshot",
-    "baichuan",
-    "ai21",
-];
-
-#[derive(Debug, Clone, Copy)]
-pub(crate) struct AdminProviderPoolConfig {
-    pub(crate) lru_enabled: bool,
-    pub(crate) cost_window_seconds: u64,
-    pub(crate) cost_limit_per_key_tokens: Option<u64>,
-}
-
-#[derive(Debug, Default)]
-pub(crate) struct AdminProviderPoolRuntimeState {
-    pub(crate) total_sticky_sessions: usize,
-    pub(crate) sticky_sessions_by_key: BTreeMap<String, usize>,
-    pub(crate) cooldown_reason_by_key: BTreeMap<String, String>,
-    pub(crate) cooldown_ttl_by_key: BTreeMap<String, u64>,
-    pub(crate) cost_window_usage_by_key: BTreeMap<String, u64>,
-    pub(crate) lru_score_by_key: BTreeMap<String, f64>,
-}