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>

assets/js/korrespond.js

@@ -382,6 +382,9 @@
     }
 
     setStatus(t('done_summary', { s: Math.round((finalResult.latency_ms || 0) / 1000), n: (finalResult.cited_law || []).length }), 'ok');
+    if (typeof finalResult.balance === 'number' && typeof window.dbnUpdateCredits === 'function') {
+      window.dbnUpdateCredits(finalResult.balance);
+    }
     lastFinal = finalResult;
     renderFinal(finalResult);
     pendingClarifications = {}; // reset for next run
@@ -487,6 +490,9 @@
     }
 
     setStatus(t('refined_summary', { s: Math.round((finalResult.latency_ms || 0) / 1000), n: (finalResult.cited_law || []).length, jur: jurLabel }), 'ok');
+    if (typeof finalResult.balance === 'number' && typeof window.dbnUpdateCredits === 'function') {
+      window.dbnUpdateCredits(finalResult.balance);
+    }
     renderRefined(finalResult);
   }