feat: Integrate with Sentry feature flag Change Tracking

[emyller]

Read more: https://docs.sentry.io/product/issues/issue-details/feature-flags/

---

Thanks for submitting a PR! Please check the boxes below:

• I have added information to docs/ if required so people know about the feature!
• I have filled in the "Changes" section below?
• I have filled in the "How did you test this code" section below?
• I have used a Conventional Commit title for this Pull Request

Changes

• Introduce a new endpoint to set up a Sentry feature flags webhook.
• Send feature flag updates to Sentry (Change Tracking).

How did you test this code?

• Unit tests.
• Integration tests.
• Manual tests with a local web app, a Flagsmith account, and a Sentry account.

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3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
docs	⬜️ Ignored (Inspect)	Visit Preview		Jun 16, 2025 4:02pm
flagsmith-frontend-preview	⬜️ Ignored (Inspect)	Visit Preview		Jun 16, 2025 4:02pm
flagsmith-frontend-staging	⬜️ Ignored (Inspect)	Visit Preview		Jun 16, 2025 4:02pm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.72%. Comparing base (c1eed05) to head (3439821).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5531      +/-   ##
==========================================
+ Coverage   97.69%   97.72%   +0.02%     
==========================================
  Files        1247     1255       +8     
  Lines       44249    44480     +231     
==========================================
+ Hits        43231    43467     +236     
+ Misses       1018     1013       -5     

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[khvn26]

LGTM 👍