bug(ios): opening KMP as external file did not display keyboard after installation

I tested this issue in the "Keyman-18.0.219-beta-test-13548" build(20/03/2025) on iPhone 13 (iOS version17.4). Here I am sharing my observation.

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* **TEST_INSTALL_FROM_SITE (failed):**
1. Installed the "Keyman-18.0.219.dmg" file from this PR build.
2. Open the Keyman app.
3. Checked the "Enable Keyman as system-wide keyboard". Set the keyboard as the default keyboard box on the settings page.
4. Select the "SIL_Euro_Latin" keyboard and set as English.
5. Download the "Sil_IPA" file from the "jahorton.github.io" website.
6. Navigate to the downloader folder.
7. Click on the "sil_ipa.kmp" file and then select the Keyman app.
8. Install the sil_ipa keyboard.
Actual Results: The Keyman app launched automatically, but no keyboard was displayed when I clicked on it.
sil_ipa keyboard appeared after I closed and reloaded the Keyman app.
Please have a look at the attached video file.
https://github.com/user-attachments/assets/08b62b46-bbfd-4b21-8380-d6d198d9a1ab

_Originally posted by @dinakaranr in https://github.com/keymanapp/keyman/issues/13548#issuecomment-2739720726_

I did manage to trigger this once personally. That said, I was able to confirm the keyboard did install and that the test error reported above is a separate issue.