feat: add "Create Spec" button and fix Windows asyncio subprocess

UI Changes:
- Add "Create Spec with AI" button in empty kanban when project has no spec
- Button opens SpecCreationChat to guide users through spec creation
- Shows in Pending column when has_spec=false and no features exist

Windows Fixes:
- Fix asyncio subprocess NotImplementedError on Windows
- Set WindowsProactorEventLoopPolicy in server/__init__.py
- Remove --reload from uvicorn (incompatible with Windows subprocess)
- Add process cleanup on startup in start_ui.bat

Spec Chat Improvements:
- Enable full tool access (remove allowed_tools restriction)
- Add "user" to setting_sources for global skills access
- Use bypassPermissions mode for auto-approval
- Add WebFetch/WebSearch auto-approve hook

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

start_ui.bat

@@ -9,6 +9,12 @@ echo   AutoCoder UI
 echo ====================================
 echo.
 
+REM Kill any existing processes on port 8888
+echo Cleaning up old processes...
+for /f "tokens=5" %%a in ('netstat -aon ^| findstr ":8888" ^| findstr "LISTENING"') do (
+    taskkill /F /PID %%a >nul 2>&1
+)
+
 REM Check if Python is available
 where python >nul 2>&1
 if %ERRORLEVEL% neq 0 (