Clipboard manager in Magikeyboard

### Checks

- [x] I have read the Wiki, searched the open issues, and still think this is a new feature.

### Explain the problem clearly and succinctly:

The Keep keyboard is in the foreground. On some websites/apps, after entering a phone number, a verification code is received, which my phone automatically copies to the system clipboard. However, long-pressing the verification code text input box (each number has its own input box) has no effect. I have to open Messages again to view the verification code, then switch to the default keyboard to enter it. After entering the code, I have to switch back to the Keep keyboard to fill in other fields.

### Describe the solution you'd like:

Add a button in a certain location in the screenshot to bring up the system clipboard, reducing the number of times you need to switch.

### Describe alternatives you've considered:

_No response_

### Additional context:

Chinese internet companies mostly use phone numbers to receive verification codes. 2FA is almost never used. This is for real-name registration and monitoring.

Android 11

linked to https://github.com/Kunzisoft/KeePassDX/issues/2388#issuecomment-5465710069

Start by locating the Magikeyboard implementation and reviewing the linked KeePassDX issue for related context on clipboard access. The change is complete when a keyboard button can bring up the system clipboard while entering a verification code, without switching keyboards.

Written by the indexing model from the issue text.