fix: parse site24x7 LABELS as dict for AlertDto compatibility

[Jleee713]

Closes #6527

📑 Description

Fix Site24X7Provider._format_alert incorrectly parsing the LABELS webhook field as a list instead of a dict.

AlertDto.labels is typed as dict | None, so passing a list caused labels to be silently dropped by pydantic on alert ingestion.

• Parse LABELS string (e.g. "env:prod,team:sre") into a dict ({"env": "prod", "team": "sre"})
• Handle pre-parsed dict payloads passthrough
• Fall back to {} for empty/missing values

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information

Before: LABELS was split into a list of strings and passed to AlertDto.labels, which expects a dict — causing labels to never appear on alerts.

After: LABELS is parsed as key:value pairs into a dict. Keys without a : separator are stored with an empty string value.

[CLAassistant]

All committers have signed the CLA.

[shahargl]

lgtm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 30.54%. Comparing base (5fc042d) to head (cf72fde).
⚠️ Report is 45 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6526       +/-   ##
===========================================
- Coverage   46.41%   30.54%   -15.88%     
===========================================
  Files         176      101       -75     
  Lines       18443    11694     -6749     
===========================================
- Hits         8561     3572     -4989     
+ Misses       9882     8122     -1760     

☔ View full report in Codecov by Sentry.
📢 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.

[ghost]

💪 Fantastic work @Jleee713! Your very first PR to keep has been merged! 🎉🥳

You've just taken your first step into open-source, and we couldn't be happier to have you onboard. 🙌
If you're feeling adventurous, why not dive into another issue and keep contributing? The community would love to see more from you! 🚀

For any support, feel free to reach out on the community: https://slack.keephq.dev. Happy coding! 👩‍💻👨‍💻