Organize readme features section with logical subsections

[Copilot]

Finalizes punkyard's documentation work from PR #6011, implementing the maintainer-approved reorganization of the "And much more" expandable section.

Changes

• Reorganized the flat feature list into 8 logical subsections within the <details> block:

  • User-Friendly Web Interface
  • Daily Backup and Easy Restore
  • Performance Optimizations
  • Security
  • Compatibility
  • Extensibility
  • Network and System
  • Container Management

• All original content preserved; no additions or removals

• Initial "Included are:" list unchanged per maintainer feedback

Before/After

Before: ~60 bullet points in a flat list

After:

<details><summary>And much more:</summary>

### User-Friendly Web Interface
- Simple web interface included...
- [Easy updates included]...

### Daily Backup and Easy Restore
- Daily backups can be enabled...

### Performance Optimizations
- APCu as local cache
- Redis as distributed cache...
...
</details>

Original prompt

i want to finelise my contribution to nextcloud all in one

---

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[punkyard]

@copilot does it mean it's in the admin hands - i'm not going to receive messages anymore about it through the github mobile app?
like:

• run succeeded main 37305b1
• run cancelled dependency updates main 37305b1
  10 times a day

[Copilot]

@copilot does it mean it's in the admin hands - i'm not going to receive messages anymore about it through the github mobile app?
like:

• run succeeded main 37305b1...

The PR is now ready for the maintainer to review and merge. You may still receive notifications for this PR since you're subscribed to it. To stop receiving notifications, you can click "Unsubscribe" on the right sidebar of the PR page, or adjust your notification settings in GitHub Settings > Notifications. The workflow run notifications (run succeeded/cancelled) are typically for your own fork's actions - you can disable those in your fork's Settings > Actions or by going to the Actions tab and adjusting the notification preferences.