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>

api/ask.php

@@ -5,6 +5,9 @@ require_once __DIR__ . '/../includes/LegalTools.php';
 
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
+$ftUid = dbnToolsFreeTierCheck('ask');
+$ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'ask');
+if ($ftRemaining >= 0) { header('X-Credits-Remaining: ' . $ftRemaining); }
 $input = dbnToolsJsonInput(25000);
 $language = dbnToolsNormalizeLanguage($input['language'] ?? 'en');
 

api/barnevernet.php

@@ -6,6 +6,8 @@ require_once __DIR__ . '/../includes/BvjAnalyzerAgent.php';
 
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
+$ftUid = dbnToolsFreeTierCheck('barnevernet');
+$ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'barnevernet');
 
 @ini_set('output_buffering', '0');
 @ini_set('zlib.output_compression', '0');
@@ -16,6 +18,7 @@ ob_implicit_flush(true);
 header('Content-Type: application/x-ndjson; charset=utf-8');
 header('Cache-Control: no-store');
 header('X-Accel-Buffering: no');
+if ($ftRemaining >= 0) { header('X-Credits-Remaining: ' . $ftRemaining); }
 
 $language  = 'en';
 $startTime = microtime(true);

api/deep-research.php

@@ -6,6 +6,8 @@ require_once __DIR__ . '/../includes/DeepResearchAgent.php';
 
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
+$ftUid = dbnToolsFreeTierCheck('deep-research');
+$ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'deep-research');
 
 // Stream-friendly response — defeat output buffering so the user's browser
 // receives progress events while the agent runs (can take 60-180s for
@@ -19,6 +21,7 @@ ob_implicit_flush(true);
 header('Content-Type: application/x-ndjson; charset=utf-8');
 header('Cache-Control: no-store');
 header('X-Accel-Buffering: no');
+if ($ftRemaining >= 0) { header('X-Credits-Remaining: ' . $ftRemaining); }
 
 $language = 'en';
 $startTime = microtime(true);

api/extract.php

@@ -5,6 +5,9 @@ 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'])) {

api/redact.php

@@ -5,6 +5,9 @@ require_once __DIR__ . '/../includes/LegalTools.php';
 
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
+$ftUid = dbnToolsFreeTierCheck('redact');
+$ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'redact');
+if ($ftRemaining >= 0) { header('X-Credits-Remaining: ' . $ftRemaining); }
 $input = dbnToolsJsonInput(400000);
 
 dbnToolsWithTelemetry('redact', '', function () use ($input): array {

api/timeline.php

@@ -5,6 +5,9 @@ require_once __DIR__ . '/../includes/LegalTools.php';
 
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
+$ftUid = dbnToolsFreeTierCheck('timeline');
+$ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'timeline');
+if ($ftRemaining >= 0) { header('X-Credits-Remaining: ' . $ftRemaining); }
 $input = dbnToolsJsonInput(400000);
 $language = dbnToolsNormalizeLanguage($input['language'] ?? 'en');
 

api/transcribe.php

@@ -5,6 +5,9 @@ require_once __DIR__ . '/../includes/LegalTools.php';
 
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
+$ftUid = dbnToolsFreeTierCheck('transcribe');
+$ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'transcribe');
+if ($ftRemaining >= 0) { header('X-Credits-Remaining: ' . $ftRemaining); }
 
 set_time_limit(0);
 ignore_user_abort(true);