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>

api/extract.php

@@ -6,8 +6,6 @@ require_once __DIR__ . '/../includes/bootstrap.php';
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
 $ftUid = dbnToolsFreeTierCheck('extract');
-$ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'extract');
-if ($ftRemaining >= 0) { header('X-Credits-Remaining: ' . $ftRemaining); }
 
 try {
     if (empty($_FILES['file']) || !is_array($_FILES['file'])) {
@@ -15,6 +13,11 @@ try {
     }
 
     $result = dbnToolsExtractUploadedFile($_FILES['file']);
+    $ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'extract');
+    if ($ftRemaining >= 0) {
+        header('X-Credits-Remaining: ' . $ftRemaining);
+        $result['balance'] = $ftRemaining;
+    }
     dbnToolsRespond($result);
 } catch (DbnToolsHttpException $e) {
     dbnToolsError($e->getMessage(), $e->status, $e->errorCode, $e->extra);