refactor: remove redundant color attributes and improve color contrast handling

feature/onboarding/src/commonMain/kotlin/bzh/ajaury/chombev/onboarding/ui/components/OnboardingInfoPage.kt

@@ -46,7 +46,6 @@ fun OnboardingInfoPage(
         Text(
             text = description,
             style = MaterialTheme.typography.bodyLarge,
-            color = MaterialTheme.colorScheme.onSurfaceVariant,
             textAlign = TextAlign.Center,
         )
     }

feature/onboarding/src/commonMain/kotlin/bzh/ajaury/chombev/onboarding/ui/components/OnboardingLevelPage.kt

@@ -51,7 +51,6 @@ fun OnboardingLevelPage(
         Text(
             text = stringResource(Res.string.onboarding_level_description),
             style = MaterialTheme.typography.bodyMedium,
-            color = MaterialTheme.colorScheme.onSurfaceVariant,
             textAlign = TextAlign.Center,
         )
         LevelOption(
@@ -110,7 +109,6 @@ private fun LevelOption(
                 Text(
                     text = description,
                     style = MaterialTheme.typography.bodySmall,
-                    color = MaterialTheme.colorScheme.onSurfaceVariant,
                 )
             }
         }

feature/onboarding/src/commonMain/kotlin/bzh/ajaury/chombev/onboarding/ui/components/OnboardingPageIndicator.kt

@@ -32,7 +32,7 @@ fun OnboardingPageIndicator(
                         if (index == currentPage) {
                             MaterialTheme.colorScheme.primary
                         } else {
-                            MaterialTheme.colorScheme.surfaceVariant
+                            MaterialTheme.colorScheme.onBackground
                         },
                     ),
             )