fix: replace complex bat scripts with Python launcher + minimal bat wrappers

Root cause: Windows batch files written with LF endings caused cmd.exe to
misparse labels and Chinese characters, producing garbled "not a command"
errors. The Python launcher avoids encoding issues entirely.

- start.py: reliable cross-platform launcher (kill ports, start 3 services,
  wait for health, print status)
- start.bat / start_all.bat: minimal 4-line ASCII wrappers
- stop.bat: inline Python for port-based process killing

stop.bat

@@ -1,27 +1,18 @@
 @echo off
-chcp 65001 >nul
-echo ================================================
-echo   停止所有 agent_jrxml 服务
-echo ================================================
-
-echo [停止] 按窗口标题清理...
-taskkill /F /FI "WINDOWTITLE eq jrxml-validator*" 2>nul
-taskkill /F /FI "WINDOWTITLE eq jrxml-api*" 2>nul
-taskkill /F /FI "WINDOWTITLE eq jrxml-frontend*" 2>nul
-
-echo [停止] 按端口清理...
-for /f "tokens=5" %%a in ('netstat -ano ^| findstr ":8000.*LISTENING"') do (
-    echo   端口 8000 - PID %%a
-    taskkill /F /PID %%a >nul 2>&1
-)
-for /f "tokens=5" %%a in ('netstat -ano ^| findstr ":8001.*LISTENING"') do (
-    echo   端口 8001 - PID %%a
-    taskkill /F /PID %%a >nul 2>&1
-)
-for /f "tokens=5" %%a in ('netstat -ano ^| findstr ":5173.*LISTENING"') do (
-    echo   端口 5173 - PID %%a
-    taskkill /F /PID %%a >nul 2>&1
-)
-
-echo 已停止
+cd /d "%~dp0"
+.venv\Scripts\python.exe -c "
+import os, signal, subprocess
+ports = (8000, 8001, 5173)
+for port in ports:
+    try:
+        r = subprocess.run(['netstat', '-ano'], capture_output=True, text=True)
+        for line in r.stdout.splitlines():
+            if f':{port}' in line and 'LISTENING' in line:
+                pid = int(line.split()[-1])
+                print(f'Killing PID {pid} on port {port}')
+                os.kill(pid, signal.SIGTERM)
+    except Exception as e:
+        print(f'Port {port}: {e}')
+print('Done')
+"
 pause