feat(scripts): introduce interactive Windows batch launcher

Consolidates and replaces the simple `start_proxy.bat` files with a unified, interactive launcher (`launcher.bat`).

This new script significantly improves the Windows execution flow by:
- Providing a main menu for running, configuring, or adding credentials.
- Allowing runtime configuration of host, port, and request logging settings.
- Automatically detecting and selecting the execution mode (compiled EXE or source code).

launcher.bat

@@ -0,0 +1,185 @@
+@echo off
+setlocal enabledelayedexpansion
+
+:: Default Settings
+set "HOST=0.0.0.0"
+set "PORT=8000"
+set "LOGGING=false"
+set "EXECUTION_MODE="
+set "EXE_NAME=proxy_app.exe"
+set "SOURCE_PATH=src\proxy_app\main.py"
+
+:: --- Phase 1: Detection and Mode Selection ---
+set "EXE_EXISTS=false"
+set "SOURCE_EXISTS=false"
+
+if exist "%EXE_NAME%" (
+    set "EXE_EXISTS=true"
+)
+
+if exist "%SOURCE_PATH%" (
+    set "SOURCE_EXISTS=true"
+)
+
+if "%EXE_EXISTS%"=="true" (
+    if "%SOURCE_EXISTS%"=="true" (
+        call :SelectModeMenu
+    ) else (
+        set "EXECUTION_MODE=exe"
+    )
+) else (
+    if "%SOURCE_EXISTS%"=="true" (
+        set "EXECUTION_MODE=source"
+    ) else (
+        call :NoTargetsFound
+    )
+)
+
+if "%EXECUTION_MODE%"=="" (
+    goto :eof
+)
+
+:: --- Phase 2: Main Menu ---
+:MainMenu
+cls
+echo ==================================================
+echo      LLM API Key Proxy Launcher
+echo ==================================================
+echo.
+echo   Current Configuration:
+echo   ----------------------
+echo   - Host IP: %HOST%
+echo   - Port: %PORT%
+echo   - Request Logging: %LOGGING%
+echo   - Execution Mode: %EXECUTION_MODE%
+echo.
+echo   Main Menu:
+echo   ----------
+echo   1. Run Proxy
+echo   2. Configure Proxy
+echo   3. Add Credentials
+echo   4. Exit
+echo.
+set /p "CHOICE=Enter your choice: "
+
+if "%CHOICE%"=="1" goto :RunProxy
+if "%CHOICE%"=="2" goto :ConfigMenu
+if "%CHOICE%"=="3" goto :AddCredentials
+if "%CHOICE%"=="4" goto :eof
+
+echo Invalid choice.
+pause
+goto :MainMenu
+
+:: --- Phase 3: Configuration Sub-Menu ---
+:ConfigMenu
+cls
+echo ==================================================
+echo      Configuration Menu
+echo ==================================================
+echo.
+echo   1. Set Host IP (Current: %HOST%)
+echo   2. Set Port (Current: %PORT%)
+echo   3. Toggle Request Logging (Current: %LOGGING%)
+echo   4. Back to Main Menu
+echo.
+set /p "CHOICE=Enter your choice: "
+
+if "%CHOICE%"=="1" (
+    set /p "HOST=Enter new Host IP: "
+    goto :ConfigMenu
+)
+if "%CHOICE%"=="2" (
+    set /p "PORT=Enter new Port: "
+    goto :ConfigMenu
+)
+if "%CHOICE%"=="3" (
+    if "%LOGGING%"=="true" (
+        set "LOGGING=false"
+    ) else (
+        set "LOGGING=true"
+    )
+    goto :ConfigMenu
+)
+if "%CHOICE%"=="4" goto :MainMenu
+
+echo Invalid choice.
+pause
+goto :ConfigMenu
+
+:: --- Phase 4: Execution ---
+:RunProxy
+cls
+set "ARGS=--host %HOST% --port %PORT%"
+if "%LOGGING%"=="true" (
+    set "ARGS=%ARGS% --enable-request-logging"
+)
+
+echo Starting Proxy...
+echo Arguments: %ARGS%
+echo.
+
+if "%EXECUTION_MODE%"=="exe" (
+    start "%EXE_NAME%" %ARGS%
+) else (
+    set "PYTHONPATH=%~dp0src;%PYTHONPATH%"
+    start python %SOURCE_PATH% %ARGS%
+)
+goto :eof
+
+:AddCredentials
+cls
+echo Launching Credential Tool...
+echo.
+
+if "%EXECUTION_MODE%"=="exe" (
+    start "%EXE_NAME%" --add-credential
+) else (
+    set "PYTHONPATH=%~dp0src;%PYTHONPATH%"
+    start python %SOURCE_PATH% --add-credential
+)
+goto :eof
+
+:: --- Helper Functions ---
+:SelectModeMenu
+cls
+echo ==================================================
+echo      Execution Mode Selection
+echo ==================================================
+echo.
+echo   Both executable and source code found.
+echo   Please choose which to use:
+echo.
+echo   1. Executable (%EXE_NAME%)
+echo   2. Source Code (%SOURCE_PATH%)
+echo.
+set /p "CHOICE=Enter your choice: "
+
+if "%CHOICE%"=="1" (
+    set "EXECUTION_MODE=exe"
+) else if "%CHOICE%"=="2" (
+    set "EXECUTION_MODE=source"
+) else (
+    echo Invalid choice.
+    pause
+    goto :SelectModeMenu
+)
+goto :end_of_function
+
+:NoTargetsFound
+cls
+echo ==================================================
+echo      Error
+echo ==================================================
+echo.
+echo   Could not find the executable (%EXE_NAME%)
+echo   or the source code (%SOURCE_PATH%).
+echo.
+echo   Please ensure the launcher is in the correct
+echo   directory or that the project has been built.
+echo.
+pause
+goto :eof
+
+:end_of_function
+endlocal

start_proxy.bat

@@ -1,3 +0,0 @@
-@echo off
-python src/proxy_app/main.py --host 0.0.0.0 --port 8000
-pause

start_proxy_debug_logging.bat

@@ -1,3 +0,0 @@
-@echo off
-python src/proxy_app/main.py --host 0.0.0.0 --port 8000 --enable-request-logging
-pause