Add one-click launcher and interactive setup wizard

- setup.py: prompts only for the values the user must choose, generates a
  random auth_key, writes config.json (backs up any existing one).
- start.bat / start.sh: create a local venv, install deps (with PyPI mirror
  fallback), run the wizard if config.json is missing, then launch main.py.
- main.py: when config.json is missing on an interactive TTY, offer to run
  the wizard instead of just exiting.
- README: new "Quick Start" section up top; manual steps kept below.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

start.bat

@@ -0,0 +1,72 @@
+@echo off
+setlocal enabledelayedexpansion
+cd /d "%~dp0"
+
+REM -------- MasterHttpRelayVPN one-click launcher (Windows) --------
+REM Creates a local virtualenv, installs deps, runs the setup wizard
+REM if needed, then starts the proxy.
+
+set "VENV_DIR=.venv"
+set "PY="
+
+where py >nul 2>&1
+if %errorlevel%==0 (
+    set "PY=py -3"
+) else (
+    where python >nul 2>&1
+    if %errorlevel%==0 (
+        set "PY=python"
+    )
+)
+
+if "%PY%"=="" (
+    echo [X] Python 3.10+ was not found on PATH.
+    echo     Install from https://www.python.org/downloads/ and re-run this script.
+    pause
+    exit /b 1
+)
+
+if not exist "%VENV_DIR%\Scripts\python.exe" (
+    echo [*] Creating virtual environment in %VENV_DIR% ...
+    %PY% -m venv "%VENV_DIR%"
+    if errorlevel 1 (
+        echo [X] Failed to create virtualenv.
+        pause
+        exit /b 1
+    )
+)
+
+set "VPY=%VENV_DIR%\Scripts\python.exe"
+
+echo [*] Installing dependencies ...
+"%VPY%" -m pip install --disable-pip-version-check -q --upgrade pip >nul
+"%VPY%" -m pip install --disable-pip-version-check -q -r requirements.txt
+if errorlevel 1 (
+    echo [!] PyPI install failed. Retrying via runflare mirror ...
+    "%VPY%" -m pip install --disable-pip-version-check -q -r requirements.txt ^
+        -i https://mirror-pypi.runflare.com/simple/ ^
+        --trusted-host mirror-pypi.runflare.com
+    if errorlevel 1 (
+        echo [X] Could not install dependencies.
+        pause
+        exit /b 1
+    )
+)
+
+if not exist "config.json" (
+    echo [*] No config.json found — launching setup wizard ...
+    "%VPY%" setup.py
+    if errorlevel 1 (
+        echo [X] Setup cancelled.
+        pause
+        exit /b 1
+    )
+)
+
+echo.
+echo [*] Starting MasterHttpRelayVPN ...
+echo.
+"%VPY%" main.py %*
+set "RC=%errorlevel%"
+if not "%RC%"=="0" pause
+exit /b %RC%