Fix: Add PHP 7.4 compatibility

- Changed PHP min-version from 8.0 to 7.4 in appinfo/info.xml
- Replaced all str_contains() calls with strpos() !== false
  - GoogleAnalyticsService.php: 1 instance
  - LLMService.php: 6 instances
- Verified no other PHP 8.0+ features in use
- Plugin now compatible with PHP 7.4 and PHP 8.0+

analytics-hub/lib/Service/GoogleAnalyticsService.php

@@ -176,7 +176,7 @@ class GoogleAnalyticsService {
             $this->logger->error("Token refresh failed: {$e->getMessage()}");
 
             // Check if it's an expired token error
-            if (str_contains($e->getMessage(), 'invalid_grant')) {
+            if (strpos($e->getMessage(), 'invalid_grant') !== false) {
                 throw new TokenExpiredException('Refresh token expired - re-run OAuth setup');
             }