fix: await DOM flush before rendering snapshot comparison

[andypalmi]

Summary

• Snapshot comparison rendering was broken: ports appeared at the top-left corner of nodes and wires were misaligned
• Root cause: v-show="!loading" hides the container with display: none. After setting loading = false, Vue hasn't flushed the DOM update yet, so flowRenderer.compare() runs while the SVG is still inside a display: none ancestor — getBBox() returns zeros for all elements
• Fix: await this.$nextTick() after loading = false to ensure the DOM is updated before rendering

Test plan

• Open a snapshot comparison dialog with two snapshots that have differing nodes
• Verify nodes render with correct port positions (input on left, output on right)
• Verify wires connect between ports, not from node top-left corners

[andypalmi]

Before

After

@hardillb Finally found the culprit

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.66%. Comparing base (d6d525f) to head (bec0f28).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7398   +/-   ##
=======================================
  Coverage   76.66%   76.66%           
=======================================
  Files         410      410           
  Lines       20874    20874           
  Branches     5066     5066           
=======================================
  Hits        16004    16004           
  Misses       4870     4870           

Flag	Coverage Δ
backend	76.66% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.