fix(myTischtennis): improve error handling for Playwright login and account verification

- Enhanced error handling in MyTischtennisClient and MyTischtennisService to provide clearer feedback when browser executables are missing.
- Updated responses to include specific error messages and status codes, improving user guidance for setup requirements.
- Refactored MyTischtennisDialog and MyTischtennisAccount components to handle API response errors more effectively, ensuring robust login and account management processes.

backend/clients/myTischtennisClient.js

@@ -520,10 +520,17 @@ class MyTischtennisClient {
         cookie
       };
     } catch (error) {
-      console.error('[myTischtennisClient.playwright] Browser login failed:', error?.message || error);
+      const rawMessage = String(error?.message || error || 'Playwright-Login fehlgeschlagen');
+      const isMissingBrowserExecutable = /Executable doesn't exist|download new browsers|playwright install/i.test(rawMessage);
+      const normalizedError = isMissingBrowserExecutable
+        ? 'Playwright-Browser ist auf dem Server nicht installiert. Bitte "npx playwright install chromium" ausführen.'
+        : rawMessage;
+      console.error('[myTischtennisClient.playwright] Browser login failed:', normalizedError);
       return {
         success: false,
-        error: error?.message || 'Playwright-Login fehlgeschlagen'
+        error: normalizedError,
+        requiresSetup: isMissingBrowserExecutable,
+        status: isMissingBrowserExecutable ? 503 : 400
       };
     } finally {
       if (context) {