Add NOK pricing catalog, credit ledger, success-based charging, and tier-gated model routing

- PricingCatalog.php: single source of truth for plans (free/plus/pro), top-ups,
  Stripe price env keys, tool costs (0–6 credits), STT variable billing, feature limits
- FreeTier.php: monthly-first credit deduction, ledger (user_tool_credit_ledger),
  STT reservation/settle/release, monthly reset, trial logic
- StripeClient.php: canonical SKUs (plus/pro/topup_100/300/1000), legacy aliases kept
- stripe-checkout.php: subscription vs payment mode, trial gating, catalog metadata
- stripe-webhook.php: idempotent via stripe_events, handles subscription lifecycle +
  invoice.paid renewal + one-time topup credit grants
- All API tools: success-based credit deduction (check before, charge after)
- transcribe.php: file-size heuristic reservation, settle from actual provider duration
- ask.php + LegalTools.php: ToolModels engine resolution — Pro gets gpt-4o
- KorrespondAgent.php + korrespond.php: tier-gated draft deployment —
  Free/Plus gets gpt-4o-mini, Pro gets gpt-4o
- pricing.php: NOK-only, plan cards, top-up packs, Organisation contact card,
  tool cost table, separate monthly/prepaid balance display
- 003_pricing_credit_catalog.sql: ledger and STT reservation tables

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

billing.php

@@ -3,6 +3,7 @@ declare(strict_types=1);
 
 require_once __DIR__ . '/includes/bootstrap.php';
 require_once __DIR__ . '/includes/FreeTier.php';
+require_once __DIR__ . '/includes/PricingCatalog.php';
 
 if (!dbnToolsIsAuthenticated()) {
     header('Location: /?return=' . urlencode('/billing.php'));
@@ -28,12 +29,8 @@ $storageMb = round($detail['storage_used_bytes'] / 1048576, 1);
 $quotaMb = $detail['storage_quota_bytes'] > 0 ? round($detail['storage_quota_bytes'] / 1048576, 0) : 0;
 $storagePct = $quotaMb > 0 ? min(100, round(($storageMb / $quotaMb) * 100)) : 0;
 
-$tierLabels = [
-    'free' => 'Gratis',
-    'plus' => 'Plus',
-    'pro' => 'Pro Familie',
-    'caveau' => 'CaveauAI',
-];
+$tierLabels = array_map(static fn(array $plan): string => (string)$plan['name'], PricingCatalog::plans());
+$tierLabels['caveau'] = 'CaveauAI';
 
 // Recent usage
 $db = dbnmDb();
@@ -125,7 +122,7 @@ $status = (string)($_GET['status'] ?? '');
             <h2>Tilgjengelige kreditter</h2>
             <p class="balance-big"><?= number_format($effective, 0, ',', ' ') ?></p>
             <p class="balance-break">
-                <?= (int)$detail['balance'] ?> månedlige · <?= (int)$detail['bonus_balance'] ?> bonus
+                <?= (int)$detail['balance'] ?> månedlige · <?= (int)$detail['bonus_balance'] ?> forhåndsbetalte
             </p>
         </div>