test: add missing-key import automation test

[svienot]

Description:

Add automation test for the following release-blocker test case:

• 3.2.18 User can import an external private key for a missing key slot

The flow implemented by the test is:

• generate an ED25519 key pair
• Import the private key through the UI in Organization mode.
• Delete only the local KeyPair through a direct access to the local database to provoque the 'missing key' situation
• Toggle Personal → Organization mode to refresh state.
• Restore the private key through the UI.

Related issue(s):

Fixes #3229

Note: the first part of the issue was previously addressed by PR #3362

[swirlds-automation]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.98%. Comparing base (5cd0f09) to head (203d401).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3366   +/-   ##
=======================================
  Coverage   99.98%   99.98%           
=======================================
  Files         213      213           
  Lines        6699     6699           
  Branches     1209     1237   +28     
=======================================
  Hits         6698     6698           
  Misses          1        1           

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