chore: partially rename services to apps in UI and code - WPB-21441

[caldrian]

WPB-21441 [iOS] [Integration] Toggle Apps in Conversation Flow

Issue

Currently the group creation dialog doesn't show the allow-apps toggle and doesn't consider the feature flag. This PR fixes it. It also renames services to apps in the codebase.

Testing

Open the create conversation screen and check that the "Allow Apps" toggle is only visible if the feature flag is enabled.

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Checklist

• [ ] Title contains a reference JIRA issue number like [WPB-XXX].
• [ ] Description is filled and free of optional paragraphs.
• [ ] Adds/updates automated tests.

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UI accessibility checklist

If your PR includes UI changes, please utilize this checklist:

• [ ] Make sure you use the API for UI elements that support large fonts.
• [ ] All colors are taken from WireDesign.ColorTheme or constructed using WireDesign.BaseColorPalette.
• [ ] New UI elements have Accessibility strings for VoiceOver.