Fix empty proxy sources (empty pool), first-run bat, elite hint

- load_settings/sanitize_settings: treat sources=[] as invalid; restore defaults (all([]) was true)
- _build_pool: defensive default sources + clearer empty-fetch log; elite-only empty fetch message
- FirstRun_Build_And_Install.bat: Python check + setup_and_build.ps1
- README + test for empty sources sanitize

Made-with: Cursor

FirstRun_Build_And_Install.bat

@@ -0,0 +1,31 @@
+@echo off
+setlocal
+title Proxy God — first-time build
+cd /d "%~dp0"
+
+echo.
+echo  === Proxy God: upgrade pip, install deps, build exe, Desktop shortcut ===
+echo.
+
+where py >nul 2>nul && py -3 -c "import sys; assert sys.version_info>=(3,10)" 2>nul && goto RUN
+where python >nul 2>nul && python -c "import sys; assert sys.version_info>=(3,10)" 2>nul && goto RUN
+
+echo  [X] Python 3.10+ not found on PATH.
+echo      winget install Python.Python.3.12 --accept-package-agreements --accept-source-agreements
+echo      Or https://www.python.org/downloads/  ^(enable "Add python.exe to PATH"^)
+echo.
+pause
+exit /b 1
+
+:RUN
+powershell -NoProfile -ExecutionPolicy Bypass -File "%~dp0scripts\setup_and_build.ps1"
+if errorlevel 1 (
+  echo.
+  echo  Build failed — see messages above.
+  pause
+  exit /b 1
+)
+echo.
+echo  === Done. Use Desktop: "Proxy God.lnk" ===
+pause
+endlocal