feat(login): three real EA2-seeded personas as quick-switch chips

Seeded HR/CEO/IT directors as real superuser rows in auth_service.user via
auth-service POST /api/v1/auth/register + a one-shot SQL promotion to
is_superuser=TRUE so dev-login resolves them:

  ceo-head@flow-master.ai  → Mariana Cole (Chief Executive)
  hr-head@flow-master.ai   → Aisha Khan   (HR Director)
  it-head@flow-master.ai   → Rohan Patel  (IT Director)

Login page exposes them as three QUICK PERSONA chips that prefill the
operator-id field; clicking SIGN IN AS DEVELOPER then issues a real JWT
for that persona. No mock users.

src/index.css

@@ -1296,6 +1296,41 @@ select.studio-input { background: var(--bp-paper); }
   flex-direction: column;
   gap: 12px;
 }
+.login-personas {
+  margin-top: 24px;
+  padding-top: 16px;
+  border-top: 1px solid var(--bp-navy);
+  border-top-color: color-mix(in srgb, var(--bp-navy) 20%, transparent);
+}
+.login-persona-label {
+  font-family: var(--bp-mono);
+  font-size: 10px;
+  letter-spacing: 0.1em;
+  color: var(--bp-muted);
+  margin-bottom: 8px;
+}
+.login-persona-row {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 6px;
+}
+.persona-chip {
+  flex: 1 1 auto;
+  padding: 6px 10px;
+  background: var(--bp-paper);
+  border: 1px solid var(--bp-navy);
+  color: var(--bp-navy);
+  font-family: var(--bp-mono);
+  font-size: 10px;
+  letter-spacing: 0.04em;
+  cursor: pointer;
+  transition: background 0.1s;
+}
+.persona-chip:hover:not(:disabled) {
+  background: var(--bp-amber);
+  color: var(--bp-paper);
+}
+.persona-chip:disabled { opacity: 0.5; cursor: not-allowed; }
 .sso-btn {
   display: flex;
   align-items: center;