Integrate Monolog: replace four logging systems with single PSR-3 factory

- Add monolog/monolog dependency (^3.10)  
- Create app/Logger.php central factory with channels: app, admin, error, audit
- Each channel gets RotatingFileHandler (30-day retention) with pass-through LineFormatter
  preserving existing JSON format contracts
- Rewrite AppLogger as thin facade delegating to Logger::get('app')
- Rewrite ErrorHandler::log() to delegate to Logger::get('error')
- Rewrite AdminLogger file output to delegate to Logger::get('admin'), keep DB writes
- Add Monolog file shadow to Audit via Logger::get('audit') (Option A per monolog-plan)
- Log level controlled by LOG_LEVEL env var (defaults: DEBUG in cli-server, WARNING otherwise)
- Graceful NullHandler fallback when log directory is not writable
- Update SystemController LOG_FILES: remove php_error, add app/admin/error/audit
- JSON app logs parsed to readable one-liners in the log viewer
- Remove nginx config tab (parametres + fragment + template + css)
- Friendly empty-state message when app log files don't exist yet (notYet)
- PHP tail fallback when exec() unavailable
- All 228 PHPUnit tests pass, no call sites changed

app/public/admin/parametres.php

@@ -48,11 +48,9 @@ $diskPct   = $diskInfo['pct'];
 $diskColor = SystemController::diskColor($diskPct);
 
 // ── Logs section ──────────────────────────────────────────────────────────────
-$activeTab = $_GET['tab'] ?? 'nginx_access';
-if ($activeTab === 'status') {
-    $activeTab = 'nginx_access';
-} elseif ($activeTab !== 'nginx_config' && !array_key_exists($activeTab, SystemController::LOG_FILES)) {
-    $activeTab = 'nginx_access';
+$activeTab = $_GET['tab'] ?? 'app';
+if ($activeTab === 'status' || !array_key_exists($activeTab, SystemController::LOG_FILES)) {
+    $activeTab = 'app';
 }
 
 $selectedN = isset($_GET['n']) ? (int) $_GET['n'] : 100;
@@ -60,27 +58,12 @@ if (!in_array($selectedN, SystemController::ALLOWED_LINES, true)) {
     $selectedN = 100;
 }
 
-$logLines    = null;
-$logError    = null;
-$logFileMeta = null;
-
-$nginxConfigLines  = null;
-$nginxConfigSource = null;
-$nginxConfigError  = null;
-$nginxConfigMeta   = null;
-
-if ($activeTab === 'nginx_config') {
-    $nginxData         = $_controller->getNginxConfigData();
-    $nginxConfigLines  = $nginxData['lines'];
-    $nginxConfigSource = $nginxData['source'];
-    $nginxConfigMeta   = $nginxData['meta'];
-    $nginxConfigError  = $nginxData['error'];
-} else {
-    $logData     = $_controller->getLogData($activeTab, $selectedN);
-    $logLines    = $logData['lines'];
-    $logError    = $logData['error'];
-    $logFileMeta = $logData['meta'];
-}
+$logData     = $_controller->getLogData($activeTab, $selectedN);
+$logLines    = $logData['lines'];
+$logError    = $logData['error'];
+$logFileMeta = $logData['meta'];
+$logIsJson   = $logData['isJson'] ?? false;
+$notYet      = $logData['notYet'] ?? false;
 
 $collapsed = $_COOKIE['sys_collapsed'] ?? null;
 $statusInitiallyCollapsed = $collapsed === '1';