Fix app cold start jank

[poliver]

Delay on the appIntroCompleted pref Flow causes the app intro the briefly flash (cold app start) on installations that have already completed it. This PR starts that Flow eagerly to hopefully address the issue.

Before	After
before.mp4	after.mp4

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.39%. Comparing base (9f91b73) to head (1921384).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...shtastic/core/datastore/UiPreferencesDataSource.kt	0.00%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #3492      +/-   ##
========================================
- Coverage   0.39%   0.39%   -0.01%     
========================================
  Files        302     302              
  Lines      17876   17878       +2     
  Branches    2142    2142              
========================================
  Hits          71      71              
- Misses     17789   17791       +2     
  Partials      16      16              

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