feat: 支持 uv 从 pyproject/requirements 创建虚拟环境

- 工作目录探测新增 pyproject.toml / requirements*.txt 扫描、uv 可用性与 can_create
- 新增 POST /api/v1/python/venv/create：已有虚拟环境优先复用；pyproject 走 uv sync，requirements 走 uv venv + uv pip install，并使用默认 PyPI 镜像
- 编辑器在缺少虚拟环境且具备依赖文件时显示「用 uv 创建环境」；没有 uv 或没有依赖文件时明确报错
- 解释器字段改为可选，留空由服务端默认 python.exe 并使用虚拟环境；Python 任务缺少虚拟环境/依赖文件时运行直接失败，不再回退系统解释器
- 补后端探测/创建测试、前端入口测试与 README

frontend/src/components/TaskEditorModal.tsx

@@ -1,5 +1,5 @@
 import { zodResolver } from '@hookform/resolvers/zod'
-import { useQuery } from '@tanstack/react-query'
+import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
 import {
   Button,
   Checkbox,
@@ -14,6 +14,7 @@ import {
   Text,
   Textarea,
   TextButton,
+  toast,
 } from '@stash/ui'
 import { useEffect, useRef, useState, type ReactNode } from 'react'
 import {
@@ -25,6 +26,7 @@ import {
 } from 'react-hook-form'
 import {
   ApiRequestError,
+  createPythonVenv,
   previewCron,
   probePythonVenv,
   type Task,
@@ -81,6 +83,7 @@ export function TaskEditorModal({
   const [submitError, setSubmitError] = useState<string | null>(null)
   const [cronPreviewCount, setCronPreviewCount] = useState(5)
   const [pickerOpen, setPickerOpen] = useState(false)
+  const queryClient = useQueryClient()
   // 记录「自动填入」的虚拟环境目录：用户手动改过就不再覆盖；
   // 工作目录变化时只有仍等于该值的字段会被清掉，交给新目录重新探测。
   const autoVenvRef = useRef('')
@@ -155,7 +158,7 @@ export function TaskEditorModal({
       probePythonVenv(
         {
           working_dir: debouncedWorkingDir,
-          interpreter: debouncedInterpreter,
+          interpreter: debouncedInterpreter.trim() || 'python.exe',
           venv: debouncedVenv.trim() || null,
         },
         signal,
@@ -165,6 +168,23 @@ export function TaskEditorModal({
     retry: false,
     staleTime: 15_000,
   })
+  const createVenvMutation = useMutation({
+    mutationFn: (workingDir: string) =>
+      createPythonVenv({ working_dir: workingDir }),
+    onSuccess: (probe, workingDir) => {
+      toast.success('虚拟环境已创建')
+      if (probe.venv_path) {
+        const value = venvFieldValue(workingDir, probe.venv_path)
+        autoVenvRef.current = value
+        setValue('script.venv', value, {
+          shouldDirty: true,
+          shouldValidate: true,
+        })
+      }
+      void queryClient.invalidateQueries({ queryKey: ['python-venv'] })
+    },
+    onError: (error) => toast.error(error.message),
+  })
   const linkedVenv = venvProbe.data?.status === 'linked' ? venvProbe.data : null
   const previewVirtualEnv =
     scriptPreview.venv.trim() || linkedVenv?.venv_path || ''
@@ -497,15 +517,16 @@ export function TaskEditorModal({
                 />
               </FormField>
               <FormField
-                label="解释器"
+                label="解释器（可选）"
                 htmlFor="task-interpreter"
+                hint="Python 项目留空即可，自动使用虚拟环境里的 Python；Node / Shell 等再填"
                 error={errors.script?.interpreter?.message}
               >
                 <Input
                   id="task-interpreter"
                   {...register('script.interpreter')}
                   className="mono-input"
-                  placeholder="python.exe"
+                  placeholder="留空自动使用虚拟环境 Python"
                 />
               </FormField>
             </div>
@@ -515,6 +536,10 @@ export function TaskEditorModal({
               probe={venvProbe.data}
               pending={venvProbe.isPending}
               failed={venvProbe.isError}
+              creating={createVenvMutation.isPending}
+              onCreate={() =>
+                createVenvMutation.mutate(scriptPreview.working_dir.trim())
+              }
             />
 
             <FormField
@@ -865,6 +890,8 @@ interface VenvDetectorBarProps {
   probe: VenvProbeResponse | undefined
   pending: boolean
   failed: boolean
+  creating: boolean
+  onCreate: () => void
 }
 
 function VenvDetectorBar({
@@ -872,6 +899,8 @@ function VenvDetectorBar({
   probe,
   pending,
   failed,
+  creating,
+  onCreate,
 }: VenvDetectorBarProps) {
   if (!workingDir.trim()) {
     return (
@@ -926,12 +955,31 @@ function VenvDetectorBar({
   }
 
   if (probe.status === 'missing') {
+    if (probe.can_create) {
+      return (
+        <div className="env-detector-bar" role="status">
+          <div className="env-detector-message">
+            <span className="env-status-badge warn">● {probe.message}</span>
+            <span className="env-detector-hint">
+              {probe.has_pyproject
+                ? 'pyproject.toml'
+                : probe.requirements_files.join(' · ')}
+            </span>
+          </div>
+          <Button
+            size="sm"
+            variant="secondary"
+            loading={creating}
+            onClick={onCreate}
+          >
+            用 uv 创建环境
+          </Button>
+        </div>
+      )
+    }
     return (
       <div className="env-detector-bar" role="status">
-        <span className="env-status-badge ok">
-          ● 使用系统解释器: <code>{probe.display_path}</code>
-        </span>
-        <span className="env-detector-hint">{probe.message}</span>
+        <span className="env-status-badge danger">● {probe.message}</span>
       </div>
     )
   }