[iOS] Capture ui_sid from DPoP token response and use it in mainSid

[wmathurin]

Summary

• Adds uiSid property to SFOAuthCredentials (public readonly in .h, readwrite in +Internal.h)
• Persists uiSid to the keychain in SFOAuthKeychainCredentials under com.salesforce.mobilesdk.oauth.uiSid
• In updateCredentials:, reads ui_sid from the token endpoint response, guarded on tokenType == "dpop"
• Updates mainSid getter: returns uiSid if present, otherwise falls back to existing logic (parentSid for jwt, accessToken otherwise)
• Adds 4 unit tests in SFOAuthCredentialsTests.m

Dependencies

This PR depends on (already merged):

• SalesforceMobileSDK-iOS#4153 — [iOS] Move mainSid calculation to SFOAuthCredentials ✅

Related PRs (same feature):

• SalesforceMobileSDK-Android#3019 — [Android] Capture ui_sid from DPoP token response and use it in mainSid
• SalesforceMobileSDK-Android#3017 — [Android] Move mainSid calculation to UserAccount
• SalesforceMobileSDK-iOS-Hybrid#323 — [iOS-Hybrid] Use creds.mainSid in SalesforceWebViewCookieManager

Tracking

• W-24024985 — [iOS] Capture ui_sid from token endpoint and use it in mainSid
• Fixes W-23984602

[github-actions]

	1 Warning
⚠️	Static Analysis found an issue with one or more files you modified. Please fix the issue(s).

Clang Static Analysis Issues

File	Type	Category	Description	Line	Col
SFOAuthCredentials	Dereference of null pointer	Logic error	Access to instance variable '_credentialsChangeSet' results in a dereference of a null pointer (loaded from variable 'self')	200	27
SFOAuthCredentials	Nullability	Memory error	nil passed to a callee that requires a non-null 1st parameter	306	20
SFOAuthKeychainCredentials	Dead initialization	Unused code	Value stored to 'result' during its initialization is never read	182	26

Generated by 🚫 Danger

[github-actions]

	Tests	Passed	Skipped	Failed ❌️
AuthFlowTester UI Test Results all	1 ran			1 ❌

Test	Result
AuthFlowTester UI Test Results all
AuthFlowTesterUITests.xctest
LegacyLoginTests.testCAOpaque_DefaultScopes_WebServerFlow()	❌ failure

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.44%. Comparing base (33d3b55) to head (c69e084).
⚠️ Report is 5 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #4154      +/-   ##
==========================================
- Coverage   67.46%   67.44%   -0.02%     
==========================================
  Files         254      254              
  Lines       22859    22868       +9     
==========================================
+ Hits        15422    15424       +2     
- Misses       7437     7444       +7     

Components	Coverage Δ
Analytics	70.78% <ø> (ø)
Common	70.88% <ø> (ø)
Core	61.10% <100.00%> (-0.03%)	⬇️
SmartStore	73.45% <ø> (ø)
MobileSync	88.84% <ø> (ø)

Files with missing lines	Coverage Δ
...lesforceSDKCore/Classes/OAuth/SFOAuthCredentials.m	92.13% <100.00%> (+0.13%)	⬆️
...SDKCore/Classes/OAuth/SFOAuthKeychainCredentials.m	93.02% <100.00%> (+0.34%)	⬆️

... and 1 file with indirect coverage changes

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[github-actions]

	Tests	Passed ✅	Skipped	Failed
SalesforceSDKCore iOS ^18 Test Results	1015 ran	1015 ✅

Test	Result
No test annotations available

[sfdctaka]

LGTM!