feat: free-tier credit system + Syttende Mai access for Google users

- FreeTier.php: credit check/deduct/reset engine with hourly rate limit
- bootstrap.php: dbnmDb() singleton, dbnToolsIsFreeTier(), credit gate helpers
- index.php: store tier=free|approved in session from SSO JWT
- All 7 API endpoints: credit gate (402/429) + X-Credits-Remaining header
- layout.php: credit meta tag, JS balance var, Syttende Mai banner (05-17 only)
- tools.js: credit badge in topbar, 402 modal, 429 toast, dbnUpdateCredits()
- barnevernet.js + deep-research.js: wire 402/429 handling for NDJSON streams
- tools.css: styles for credit badge, no-credits modal, rate-limit toast

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

assets/css/tools.css

@@ -4313,3 +4313,114 @@ body {
   .site-footer__inner { grid-template-columns: 1fr; }
   .site-footer__bottom { flex-direction: column; }
 }
+
+/* ── Syttende Mai banner ──────────────────────────────────────────────────── */
+.syttende-mai-banner {
+  background: #ba0c2f;
+  color: #fff;
+  padding: 9px 20px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 12px;
+  font-size: 0.875rem;
+  font-weight: 500;
+  letter-spacing: 0.01em;
+  position: sticky;
+  top: 0;
+  z-index: 200;
+}
+.syttende-mai-close {
+  background: none;
+  border: none;
+  color: rgba(255,255,255,0.75);
+  cursor: pointer;
+  font-size: 1rem;
+  line-height: 1;
+  padding: 0 4px;
+  margin-left: 8px;
+}
+.syttende-mai-close:hover { color: #fff; }
+
+/* ── Free-tier credit badge ──────────────────────────────────────────────── */
+.credit-badge {
+  display: inline-flex;
+  align-items: center;
+  gap: 5px;
+  padding: 3px 10px;
+  border-radius: 20px;
+  font-size: 0.78rem;
+  font-weight: 600;
+  background: var(--soft-teal);
+  color: var(--teal-dark);
+  border: 1px solid rgba(15, 118, 110, 0.25);
+  white-space: nowrap;
+  cursor: default;
+}
+.credit-badge.is-low {
+  background: #fff7ed;
+  color: #92400e;
+  border-color: rgba(183, 121, 31, 0.3);
+}
+.credit-badge.is-empty {
+  background: #fff0e8;
+  color: #c2410c;
+  border-color: rgba(194, 65, 12, 0.3);
+}
+
+/* ── Credit-empty modal ───────────────────────────────────────────────────── */
+.credit-modal-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(22, 19, 15, 0.55);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 500;
+}
+.credit-modal {
+  background: var(--panel);
+  border-radius: 12px;
+  padding: 32px 28px 24px;
+  max-width: 380px;
+  width: calc(100% - 40px);
+  box-shadow: var(--shadow);
+  text-align: center;
+}
+.credit-modal__icon { font-size: 2.5rem; margin-bottom: 12px; }
+.credit-modal h3 { margin: 0 0 8px; font-size: 1.15rem; color: var(--ink); }
+.credit-modal p { color: var(--muted); font-size: 0.9rem; margin: 0 0 20px; line-height: 1.55; }
+.credit-modal__actions { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }
+.credit-modal__actions a {
+  padding: 8px 20px;
+  border-radius: 8px;
+  font-size: 0.875rem;
+  font-weight: 600;
+  text-decoration: none;
+  display: inline-block;
+}
+.credit-modal__cta { background: var(--teal); color: #fff; }
+.credit-modal__cta:hover { background: var(--teal-dark); }
+.credit-modal__dismiss { background: var(--line); color: var(--ink); }
+.credit-modal__dismiss:hover { background: #c8cdd8; }
+
+/* ── Rate-limit toast ────────────────────────────────────────────────────── */
+.credit-toast {
+  position: fixed;
+  bottom: 24px;
+  left: 50%;
+  transform: translateX(-50%);
+  background: #1b2330;
+  color: #fff;
+  padding: 10px 20px;
+  border-radius: 8px;
+  font-size: 0.875rem;
+  z-index: 500;
+  white-space: nowrap;
+  box-shadow: 0 4px 16px rgba(0,0,0,0.25);
+  animation: toastIn 0.2s ease;
+}
+@keyframes toastIn {
+  from { opacity: 0; transform: translateX(-50%) translateY(8px); }
+  to   { opacity: 1; transform: translateX(-50%) translateY(0); }
+}