feat: add management token infra and Personalize-driven variant setup

[OMpawar-21]

• Fix ManagementToken resourcePath (was pointing at /delivery_tokens
  instead of stacks/management_tokens) and ManagementTokenModel.Scope
  JSON casing ("Scope" -> "scope")
• Add Test065_Should_Create_Management_Token to create and persist a
  shared management token after stack creation
• Add Contentstack024_ManagementTokenTest.cs with full CRUD and
  negative-path integration coverage for ManagementToken
• Add PersonalizeTestHelper for driving the Personalize API to
  auto-provision real variant groups instead of relying on a
  hardcoded variant UID
• Update Contentstack021_EntryVariantTest and Contentstack022_VariantGroupTest
  to use the dynamically-created stack and management token instead of
  the static stack API key from config
• Add stack-wide content cleanup to Contentstack999_LogoutTest before logout

[github-actions]

🔒 Security Scan Results

ℹ️ Note: Only vulnerabilities with available fixes (upgrades or patches) are counted toward thresholds.

Check Type	Count (with fixes)	Without fixes	Threshold	Result
🔴 Critical Severity	0	0	10	✅ Passed
🟠 High Severity	0	0	25	✅ Passed
🟡 Medium Severity	0	0	0	✅ Passed
🔵 Low Severity	0	0	0	✅ Passed

⏱️ SLA Breach Summary

✅ No SLA breaches detected. All vulnerabilities are within acceptable time thresholds.

Severity	Breaches (with fixes)	Breaches (no fixes)	SLA Threshold (with/no fixes)	Status
🔴 Critical	0	0	15 / 30 days	✅ Passed
🟠 High	0	0	30 / 120 days	✅ Passed
🟡 Medium	0	0	90 / 365 days	✅ Passed
🔵 Low	0	0	180 / 365 days	✅ Passed

✅ BUILD PASSED - All security checks passed