fix(fips): flaky fips blackbox test and add missing curves (#3732)

2 unrelated issues:
See https://github.com/project-zot/zot/actions/runs/21336958408/job/61410298444?pr=3731 for details.
Also add missing fips curves https://cs.opensource.google/go/go/+/refs/tags/go1.25.6:src/crypto/tls/defaults_fips140.go;l=33

Signed-off-by: Andrei Aaron <andreifdaaron@gmail.com>

pkg/api/controller.go

@@ -224,8 +224,11 @@ func (c *Controller) Run() error {
 
 		// This is a subset of the default curve preferences in defaultCurvePreferencesFIPS for TLS 1.2
 		// see https://cs.opensource.google/go/go/+/refs/tags/go1.24.9:src/crypto/tls/defaults.go;l=106
+		// P-256, P-384, and P-521 are all FIPS-compliant NIST curves
 		curvePreferences := []tls.CurveID{
 			tls.CurveP256,
+			tls.CurveP384,
+			tls.CurveP521,
 		}
 		if !fips140.Enabled() {
 			// X25519 is not FIPS-compliant