PASSKEY_ORIGIN_MISMATCH when trying to add Passkey in Forkgram (Telegram fork)

### Checks

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

### Explain the problem clearly and succinctly:

I get the error "PASSKEY_ORIGIN_MISMATCH" when try to use [Forkgram](https://f-droid.org/packages/org.forkgram.messenger/) to add a Passkey via KeePassXD.

video (the sensitive parts are automatically censored, so do not wonder about the black parts):
https://github.com/user-attachments/assets/f762901d-fc01-4197-acb9-001265df2edd

(If this is just the app origin, then maybe just the name/app ID needs to be adjusted?)

### Describe what you expected to happen:

Maybe a better error?
Or could do KeePassDX anything to help n this case (see below)?

### KeePassDX version:

4.2.4

### Build:

Libre

### Database version:

no idea

### File provider (`content://` URI)

Nextcloud(?`) likely unrelated

### Android version:

15

### Android device:

Fairphone 4 (FP4)

### Additional context:

Reported "downstream": https://github.com/forkgram/TelegramAndroid/issues/360#issuecomment-3655701788

Forkgram v12.2.6.0 (63010) from F-Droid
Android 15, CalyxOS 6.10.20
with microG (but I guess this is not involved here)

---

I have no insides of whether KeePassDX has any fault here or could do something, but here some random collection of facts:
* the [maintainer of Forkgram has stated](https://github.com/forkgram/TelegramAndroid/issues/360#issuecomment-3649847217):
> No passkeys for third-party Telegram apps.
* I have no idea _why_ that is so, e.g. if KeePassDX can do something error, the error seems to be shown from the Telegram fork though, but I have no idea whether that is really the case.)
* e.g. if this is just the app origin, then maybe just the name/app ID can be adjusted/faked? By KeePassDX?
* I have tested adding the Passkey with the official Telegram app and it works there.
* [Other users](https://github.com/forkgram/TelegramAndroid/issues/360#issuecomment-3676423074) have reported it also does not work with _Bitwarden_ though with **a different error** ("Passkeys not supported for this app" and "Failed to create a passkey"). See https://github.com/bitwarden/android/issues/6164#issuecomment-3655694155 and https://github.com/AChep/keyguard-app/issues/1136#issue-3677755297

Start by reproducing passkey creation with KeePassDX 4.2.4 in Forkgram and compare it with the working official Telegram flow. Read the linked Forkgram, Bitwarden, and Keyguard reports to determine whether KeePassDX can affect the origin mismatch; done should establish a supported fix or clearly document that the incompatibility is outside KeePassDX.

Written by the indexing model from the issue text.