docs: consolidate documentation into organized structure

- Move 12 markdown files from root to docs/ subdirectories
- Organize documentation by category:
  • docs/troubleshooting/ (1 file)  - Technical troubleshooting guides
  • docs/deployment/      (4 files) - Deployment and security documentation
  • docs/guides/          (3 files) - Feature-specific guides
  • docs/planning/        (4 files) - Planning and improvement proposals

Root directory cleanup:
- Reduced from 16 to 4 markdown files in root
- Only essential project files remain:
  • CLAUDE.md (AI instructions)
  • README.md (Main project readme)
  • CLEANUP_PLAN.md (Current cleanup plan)
  • SRC_STRUCTURE_IMPROVEMENTS.md (Structure improvements)

This improves:
✅ Documentation discoverability
✅ Logical organization by purpose
✅ Clean root directory
✅ Better maintainability

src/Framework/Console/DemoCommand/ScreenDemoCommand.php

@@ -8,6 +8,7 @@ use App\Framework\Console\ConsoleCommand;
 use App\Framework\Console\ConsoleInput;
 use App\Framework\Console\ConsoleOutput;
 use App\Framework\Console\ConsoleStyle;
+use App\Framework\Console\ExitCode;
 use App\Framework\Console\Screen\ScreenType;
 use App\Framework\Core\ValueObjects\Duration;
 use App\Framework\DateTime\Timer;
@@ -20,7 +21,7 @@ final class ScreenDemoCommand
     }
 
     #[ConsoleCommand('demo:screen', 'Zeigt die verschiedenen Screen-Management-Funktionen')]
-    public function __invoke(ConsoleInput $input, ConsoleOutput $output): int
+    public function __invoke(ConsoleInput $input, ConsoleOutput $output): ExitCode
     {
         // Aktiviere interaktiven Modus
         $output->screen->setInteractiveMode(true);
@@ -58,7 +59,7 @@ final class ScreenDemoCommand
                 $output->writeError('Ungültige Auswahl!');
         }
 
-        return 0;
+        return ExitCode::SUCCESS;
     }
 
     private function demoCursor(ConsoleInput $input, ConsoleOutput $output): void