feat: support API in direct editing

[marinofaggiana]

Summary

This PR migrates document editor discovery, creation, and opening to the Nextcloud Direct Editing API while preserving the legacy Richdocuments flow for older Collabora configurations.

What changed

• Fetches and caches Direct Editing editors and creators separately from the standard server capabilities.
• Centralizes document editor availability checks and routing.
• Opens Collabora through NCViewerDirectEditing when the richdocuments Direct Editing editor is available.
• Falls back to the legacy NCViewerRichdocuments flow only when Collabora is not available through Direct Editing.
• Migrates Text and Rich Workspace operations to the Direct Editing APIs.
• Separates Direct Editing creation and template APIs from the legacy Richdocuments endpoints.
• Groups Office creation actions by provider.
• Adds Collabora creators for Document, Spreadsheet, Presentation, and Diagram.
• Supports both DirectEditingMobileInterface and RichDocumentsMobileInterface in the Direct Editing viewer.
• Handles Collabora mobile actions including sharing, pasting, inserting graphics, downloading, printing, slideshow, renaming, hyperlinks, reloading, and closing.
• Renames legacy Richdocuments components to make the distinction from Direct Editing explicit.
• Moves editor-specific availability and user-agent logic out of NCUtility.

Compatibility

• Modern Collabora installations use the Direct Editing editor identified by richdocuments.
• Older Collabora installations continue to use the legacy /apps/richdocuments/ endpoints.
• Text, OnlyOffice, EuroOffice, and Whiteboard remain Direct Editing editors.
• Existing offline and end-to-end encryption restrictions are preserved.

Dependencies

• Depends on refactor: separate Direct Editing and legacy Richdocuments APIs NextcloudKit#248.
• Uses the Collabora Direct Editing support introduced by feat(direct-editing): integrate with OCP\DirectEditing API richdocuments#5656.
• Before merging, the temporary NextcloudKit editors branch dependency must be replaced with a released version containing the required APIs.

Test plan

• Build the Nextcloud scheme locally.
• Run NextcloudUnitTests: 45 tests passed in 6 suites.
• Run SwiftLint on all changed Swift files.
• Validate the Xcode project and Git diff.
• Verify opening and creating files with legacy Collabora.
• Verify Direct Editing Collabora with Document, Spreadsheet, Presentation, and Diagram.
• Verify Text, EuroOffice, and Whiteboard.

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI