[PM-36609] Add regex manager for updating electronVersion on electron updates

[trmartin4]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-36609

📔 Objective

We currently have to manually update the electron-builder.json electronVersion for each electron update.

This PR adds in a custom regex manager to look in electron-builder.json and update the version when electron updates.

This is similar to what we do for the Rust toolchain update already.

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

Adds a Renovate custom regex manager to keep electronVersion in apps/desktop/electron-builder.json synchronized with the electron npm package. The change pairs cleanly with the existing CI verification in .github/workflows/build-desktop.yml (lines 63-73) that fails the build when these versions diverge, so automating the bump is a sound reliability improvement. The regex ("electronVersion":\s*"(?<currentValue>[\d.]+)"), the fileMatch anchor that correctly excludes electron-builder.beta.json, and the npm datasource with depName: electron all check out. Future PRs raised by this manager will be picked up by the existing electron group rule (lines 471-481) alongside electron-builder/electron-updater.

Code Review Details

No findings.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.01%. Comparing base (72f082b) to head (1446d41).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20520      +/-   ##
==========================================
- Coverage   47.02%   47.01%   -0.01%     
==========================================
  Files        3951     3951              
  Lines      119648   119648              
  Branches    18325    18325              
==========================================
- Hits        56265    56257       -8     
- Misses      59141    59150       +9     
+ Partials     4242     4241       -1     

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