fix: reduce PHPStan baseline from 82 to 67 errors

[Spomky]

Summary

• Reduce PHPStan baseline from 82 to 67 ignored errors (-15 errors, -138 lines) by fixing real type issues in the codebase
• Add proper return type annotation on WebauthnCollector::getData()
• Fix Psr18HttpClient anonymous class header types to match ResponseInterface covariance
• Add @var string[] type assertion for x5c JWT header in FidoAllianceCompliantMetadataService
• Uncomment 3rd parameter in PublicKeyCredentialCreationOptionsBuilder interface to match implementation
• Initialize attestationStatementSupportManager in CompoundAttestationStatementSupport constructor
• Make WebauthnBadge properties nullable with defaults and call parent UserBadge constructor
• Widen Doctrine type convertToDatabaseValue() param to mixed with assert() for proper contravariance

Test plan

• castor phpstan passes with no errors
• Verify existing PHPUnit tests still pass
• Verify no behavioral changes in WebauthnBadge getter methods (null check added alongside isResolved check)

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