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/transcribe.php

@@ -2,12 +2,14 @@
 declare(strict_types=1);
 
 require_once __DIR__ . '/../includes/LegalTools.php';
+require_once __DIR__ . '/../includes/FreeTier.php';
 
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
-$ftUid = dbnToolsFreeTierCheck('transcribe');
-$ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'transcribe');
-if ($ftRemaining >= 0) { header('X-Credits-Remaining: ' . $ftRemaining); }
+$ftUid = 0;
+$ftRemaining = -1;
+$sttReservationId = 0;
+$sttSettled = false;
 
 set_time_limit(0);
 ignore_user_abort(true);
@@ -92,6 +94,23 @@ $detectedMime = mime_content_type($file['tmp_name']) ?: 'application/octet-strea
 $timeOffset   = max(0.0, (float)($_POST['time_offset'] ?? 0));
 $t0           = microtime(true);
 
+$estimatedCredits = FreeTier::estimateTranscribeCreditsFromFile((string)($file['name'] ?? ''), (int)($file['size'] ?? 0));
+$ftUid = dbnToolsFreeTierCheckAmount('transcribe', $estimatedCredits);
+if ($ftUid > 0) {
+    $sttReservationId = FreeTier::createReservation($ftUid, 'transcribe', $estimatedCredits, [
+        'filename' => (string)($file['name'] ?? ''),
+        'bytes' => (int)($file['size'] ?? 0),
+        'mime' => $detectedMime,
+        'language' => $language,
+        'diarize' => $diarize,
+    ]);
+    register_shutdown_function(static function () use (&$sttSettled, $sttReservationId): void {
+        if (!$sttSettled && $sttReservationId > 0) {
+            FreeTier::releaseReservation($sttReservationId, ['reason' => 'request_ended_before_settlement']);
+        }
+    });
+}
+
 // ── Auto-cascade: Azure → GCP → Whisper GPU ───────────────────────────────────
 
 $result      = null;
@@ -186,6 +205,25 @@ $engineLabel = match($engineUsed) {
 
 // ── Log + respond ─────────────────────────────────────────────────────────────
 
+$durationSec = round((float)($result['duration_seconds'] ?? $result['duration'] ?? 0), 2);
+$creditsUsed = FreeTier::transcribeCreditsForSeconds($durationSec);
+$ftRemaining = dbnToolsFreeTierDeductAmount($ftUid, 'transcribe', $creditsUsed, [
+    'engine' => $engineUsed,
+    'duration_sec' => $durationSec,
+    'estimated_credits' => $estimatedCredits,
+    'reservation_id' => $sttReservationId,
+]);
+if ($ftRemaining >= 0) {
+    header('X-Credits-Remaining: ' . $ftRemaining);
+}
+if ($sttReservationId > 0) {
+    FreeTier::settleReservation($sttReservationId, $creditsUsed, $engineUsed, $durationSec, [
+        'estimated_credits' => $estimatedCredits,
+        'balance_after' => $ftRemaining,
+    ]);
+    $sttSettled = true;
+}
+
 dbnToolsLogMetadata([
     'tool'       => 'transcribe',
     'engine'     => $engineUsed,
@@ -203,12 +241,14 @@ dbnToolsRespond([
     'speaker_roles' => $speakerRoles,
     'num_speakers'  => $numDetected,
     'language'      => (string)($result['language'] ?? $language),
-    'duration_sec'  => round((float)($result['duration_seconds'] ?? $result['duration'] ?? 0), 2),
+    'duration_sec'  => $durationSec,
     'processing_sec'=> round((float)($result['processing_seconds'] ?? 0), 2),
     'model'         => $engineLabel,
     'engine'        => $engineUsed,
     'latency_ms'    => $latencyMs,
     'cleaned_by'    => $cleanedBy,
+    'credits_used'  => $creditsUsed,
+    'balance'       => $ftRemaining,
 ]);