feat(M45): ACME certificate profile selection, ARI RFC 9773 renumber, 45-day renewal positioning

Three related ACME ecosystem changes shipped as a single milestone:

1. ACME Certificate Profile Selection: Custom JWS-signed newOrder POST with
   `profile` field (e.g., `tlsserver`, `shortlived` for 6-day certs) bypassing
   acme.Client.AuthorizeOrder() since golang.org/x/crypto lacks profile support.
   ES256 JWS signing with kid mode, nonce management, directory discovery.
   Empty profile delegates to standard library path (zero behavior change).
   Configurable via CERTCTL_ACME_PROFILE env var. GUI: profile dropdown on
   ACME issuer config.

2. ARI RFC 9702 → 9773 Renumber: All 25+ references updated across Go source,
   docs, README, and examples. Zero remaining occurrences of RFC 9702.

3. 45-Day / Short-Lived Certificate Positioning: 5 domain tests validating
   renewal thresholds against SC-081v3 validity reduction timeline (200→100→47
   days) and Let's Encrypt 45-day/6-day profiles. ARI (RFC 9773) is the
   expected renewal path for 6-day shortlived certs.

New tests: 13 profile + 5 domain threshold + 1 frontend = 19 new tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/service/renewal_test.go

@@ -853,7 +853,7 @@ func TestProcessRenewalJob_NoCertificate(t *testing.T) {
 	}
 }
 
-// --- ARI (RFC 9702) Scheduler Integration Tests ---
+// --- ARI (RFC 9773) Scheduler Integration Tests ---
 
 func TestCheckExpiringCertificates_ARI_ShouldRenewNow(t *testing.T) {
 	t.Helper()