Add validation for maxVersion below minimum allowed TLS version

[Copilot]

The TLS config validation was checking if maxVersion < minVersion but not validating whether an explicitly set maxVersion is below the minimum allowed version (TLS 1.3). This allowed invalid configurations like WithMaxVersion(tls.VersionTLS10) to pass validation.

Changes

• Add validation in validateCommonConfig to reject maxVersion values below tlsDefaultMinVersion (TLS 1.3) when explicitly set
• Maintain existing behavior where maxVersion = 0 means "no maximum" and is allowed
• Add test cases covering the new validation logic

// Before: This would pass validation incorrectly
config, _ := New(
    WithMinVersion(tls.VersionTLS13),
    WithMaxVersion(tls.VersionTLS10), // TLS 1.0 < TLS 1.3 but wasn't caught
)

// After: Returns ErrTLSVersionTooLow
config, err := New(
    WithMinVersion(tls.VersionTLS13),
    WithMaxVersion(tls.VersionTLS10), // Now properly rejected
)

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