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/control/auth/resolution.rs

@@ -106,14 +106,14 @@ pub(in super::super) async fn resolve_control_decision_auth(
         return Ok(ControlDecisionAuthResolution::Resolved(decision));
     }
 
-    if skips_legacy_python_auth_context(&decision) {
+    if allows_missing_data_backed_auth_context(&decision) {
         return Ok(ControlDecisionAuthResolution::Resolved(decision));
     }
 
     Ok(ControlDecisionAuthResolution::Resolved(decision))
 }
 
-fn skips_legacy_python_auth_context(decision: &GatewayControlDecision) -> bool {
+fn allows_missing_data_backed_auth_context(decision: &GatewayControlDecision) -> bool {
     matches!(
         decision.route_kind.as_deref(),
         Some("chat" | "cli" | "compact")
@@ -593,7 +593,7 @@ mod tests {
             sample_snapshot("key-1", "user-1"),
         )]));
         let data = GatewayDataState::with_auth_api_key_repository_for_tests(repository.clone());
-        let state = AppState::new("http://127.0.0.1:9")
+        let state = AppState::new()
             .expect("state should build")
             .with_data_state_for_tests(data);