refactor: 移除 Python upstream 依赖，清理全部 legacy/Python 兼容层

- 移除 upstream_base_url 参数及 AETHER_GATEWAY_UPSTREAM 环境变量，gateway 不再需要指向 Python 宿主
- 删除所有 LEGACY_*/PYTHON_* 常量、路由组、header 定义及 sunset/phaseout 机制
- 将 legacy_gateway_bridge 重命名为 internal_gateway，executor 相关命名统一为 execution_runtime
- dev.sh 新增 Postgres/Redis 预检查，移除 upstream 相关启动参数和提示
- 新增 ai_public 路由处理器
- 全量适配 handler、test、state、control 等模块的命名和接口变更

apps/aether-gateway/src/ai_pipeline/planner/candidate_affinity.rs

@@ -103,7 +103,9 @@ mod tests {
     };
     use serde_json::json;
 
-    use super::*;
+    use super::{
+        prefer_local_tunnel_owner_candidates, GatewayMinimalCandidateSelectionCandidate, AppState,
+    };
     use crate::gateway::tunnel::TunnelAttachmentRecord;
     use crate::gateway::GatewayDataState;
 
@@ -245,7 +247,7 @@ mod tests {
                 .expect("local attachment should serialize"),
             ),
         ]);
-        let state = AppState::new("http://127.0.0.1:1")
+        let state = AppState::new()
             .expect("state should build")
             .with_data_state_for_tests(data_state)
             .with_tunnel_identity_for_tests("gateway-a", Some("http://gateway-a:8080"));
@@ -274,7 +276,7 @@ mod tests {
             std::sync::Arc::new(provider_catalog),
             "development-key",
         );
-        let state = AppState::new("http://127.0.0.1:1")
+        let state = AppState::new()
             .expect("state should build")
             .with_data_state_for_tests(data_state)
             .with_tunnel_identity_for_tests("gateway-a", Some("http://gateway-a:8080"));

apps/aether-gateway/src/ai_pipeline/planner/passthrough/provider/request.rs

@@ -1,4 +1,16 @@
-use super::*;
+use std::collections::BTreeMap;
+
+use serde_json::Value;
+use url::form_urlencoded;
+
+use super::{
+    apply_local_body_rules, build_antigravity_v1internal_url, build_claude_code_messages_url,
+    build_claude_messages_url, build_gemini_content_url,
+    build_kiro_generate_assistant_response_url, build_kiro_provider_request_body,
+    build_passthrough_path_url, build_vertex_api_key_gemini_content_url,
+    resolve_local_vertex_api_key_query_auth, sanitize_claude_code_request_body,
+    AntigravityRequestUrlAction, LocalSameFormatProviderFamily, LocalSameFormatProviderSpec,
+};
 
 pub(super) fn build_same_format_provider_request_body(
     body_json: &Value,

apps/aether-gateway/src/ai_pipeline/planner/standard/matrix.rs

@@ -156,7 +156,8 @@ fn build_openai_chat_request_body(
 
 #[cfg(test)]
 mod tests {
-    use super::*;
+    use super::build_standard_request_body;
+    use serde_json::json;
 
     #[test]
     fn builds_openai_chat_request_from_claude_chat_source() {

apps/aether-gateway/src/ai_pipeline/planner/standard/normalize.rs

@@ -306,7 +306,8 @@ pub(crate) fn build_cross_format_openai_cli_upstream_url(
 
 #[cfg(test)]
 mod tests {
-    use super::*;
+    use super::build_cross_format_openai_cli_request_body;
+    use serde_json::json;
 
     #[test]
     fn builds_openai_family_cross_format_request_body_from_compact_source() {

apps/aether-gateway/src/ai_pipeline/planner/standard/plan_builders.rs

@@ -1,9 +1,10 @@
-use aether_contracts::RequestBody;
+use aether_contracts::{ExecutionPlan, RequestBody};
 
-use super::augment_sync_report_context;
-use super::*;
+use super::{augment_sync_report_context, LocalStreamPlanAndReport, LocalSyncPlanAndReport};
 use crate::gateway::ai_pipeline::adaptation::surfaces::provider_adaptation_requires_eventstream_accept;
+use crate::gateway::ai_pipeline::planner::generic_decision_missing_exact_provider_request;
 use crate::gateway::provider_transport::ensure_upstream_auth_header;
+use crate::gateway::{GatewayControlSyncDecisionResponse, GatewayError};
 
 pub(crate) fn build_standard_sync_plan_from_decision(
     _parts: &http::request::Parts,