SDK-92 Fix intermittent in-app message positioning

[sumeruchat]

What

Fixes intermittent positioning issues where in-app messages configured for bottom/top/center positions display in the wrong location.

Jira ticket: SDK-92

Root Cause

viewDidLayoutSubviews() calls resizeWebView() before the webview content finishes loading. When document.body.offsetHeight is evaluated via JavaScript before the DOM is ready, it returns 0 or incorrect values, causing position calculations to fail.

The lifecycle was:

1. viewDidLoad() loads HTML into webview
2. viewDidLayoutSubviews() called (before content ready) → calculates wrong position
3. webView(_:didFinish:) called (after content ready) → recalculates, but may be too late

Solution

Added webViewDidFinishLoading flag that prevents resizeWebView() from executing in viewDidLayoutSubviews() until the webview finishes loading. This ensures position is only calculated when document.body.offsetHeight returns accurate values.

Changes

• IterableHtmlMessageViewController.swift

  • Added webViewDidFinishLoading flag (initially false)
  • Set flag to true in webView(_:didFinish:)
  • Guard viewDidLayoutSubviews() resize logic with flag check

• IterableHtmlMessageViewControllerTests.swift

  • Added testWebViewFinishLoadingFlagBehavior() to verify flag lifecycle

Impact

• Breaking changes: None
• Dependencies: None
• Performance: No impact (just defers position calculation until content is ready)

Testing

Unit tests: New test verifies the webViewDidFinishLoading flag behavior

Manual testing:

1. Create a bottom position in-app message
2. Trigger it multiple times quickly
3. Verify it always displays at the bottom (not intermittently in center/top)
4. Repeat for top and center positions

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.79%. Comparing base (8cf5fd0) to head (98c46d5).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1001      +/-   ##
==========================================
+ Coverage   70.75%   70.79%   +0.04%     
==========================================
  Files         112      112              
  Lines        9191     9197       +6     
==========================================
+ Hits         6503     6511       +8     
+ Misses       2688     2686       -2     

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