feat: 左侧导航改版与 Python 镜像管理

- 应用外壳换成 stash-ui Layout：左侧导航（任务调度 / Python 镜像）+ 页面标题区，窄屏折叠为顶部导航
- 新增 python_mirrors 表与 CRUD/设默认接口，内置清华、阿里云、中科大、PyPI 官方
- Python 脚本任务运行时注入默认镜像的 PIP_INDEX_URL / UV_INDEX_URL，任务自身环境变量优先
- 新增镜像管理页与表单，支持新增、编辑、启用/停用、设默认、删除
- 重新生成 OpenAPI 与 TS 类型；补齐后端镜像测试、前端单测与 e2e，修复窄屏页面被宽表格撑开

backend/src/runs/executor.rs

@@ -1,5 +1,5 @@
 use std::{
-    collections::HashMap,
+    collections::{BTreeMap, HashMap},
     path::{Path, PathBuf},
     process::Stdio,
     sync::{
@@ -26,7 +26,7 @@ use tokio_util::sync::CancellationToken;
 use crate::{
     error::ApiResult,
     process_job::ProcessJob,
-    python_env::prepare_script_environment,
+    python_env::{is_python_interpreter, prepare_script_environment},
     runs::{
         model::{RunStatus, RunTrigger, TaskRunResponse},
         repository,
@@ -447,11 +447,48 @@ impl TaskExecutor {
                 };
                 let mut command = Command::new(&prepared.interpreter);
                 prepared.apply(&mut command);
+
+                let mut notes = Vec::new();
+                if let Some(venv) = &prepared.virtual_env {
+                    notes.push(format!("使用 Python 虚拟环境: {}", venv.display()));
+                }
+                if is_python_interpreter(interpreter) {
+                    match crate::python_mirrors::repository::default_enabled(&self.inner.pool).await
+                    {
+                        Ok(Some(mirror)) => {
+                            if !env_has(env, "PIP_INDEX_URL") {
+                                command.env("PIP_INDEX_URL", &mirror.index_url);
+                            }
+                            if !env_has(env, "UV_INDEX_URL") {
+                                command.env("UV_INDEX_URL", &mirror.index_url);
+                            }
+                            if let Some(host) = mirror
+                                .trusted_host
+                                .as_deref()
+                                .map(str::trim)
+                                .filter(|value| !value.is_empty())
+                                && !env_has(env, "PIP_TRUSTED_HOST")
+                            {
+                                command.env("PIP_TRUSTED_HOST", host);
+                            }
+                            notes.push(format!(
+                                "Python 包镜像: {} ({})",
+                                mirror.name, mirror.index_url
+                            ));
+                        }
+                        Ok(None) => {}
+                        Err(error) => {
+                            tracing::warn!(
+                                task_id = %task.id,
+                                %error,
+                                "failed to load default python mirror"
+                            );
+                        }
+                    }
+                }
+
                 command.arg(script).args(args).current_dir(working_dir);
-                let startup_note = prepared
-                    .virtual_env
-                    .as_ref()
-                    .map(|venv| format!("使用 Python 虚拟环境: {}", venv.display()));
+                let startup_note = (!notes.is_empty()).then(|| notes.join("；"));
                 self.run_command(task, run_id, cancellation, command, startup_note)
                     .await
             }
@@ -1064,6 +1101,11 @@ async fn wait_after_termination(child: &mut Child) {
     }
 }
 
+fn env_has(env: &BTreeMap<String, String>, key: &str) -> bool {
+    env.keys()
+        .any(|candidate| candidate.eq_ignore_ascii_case(key))
+}
+
 fn sensitive_values(action: &TaskAction) -> Vec<String> {
     match action {
         TaskAction::Script { env, .. } | TaskAction::Process { env, .. } => env