v1.8.0: Refonte UX update firmware (progress bar live + streaming logs)

L'ancien flow etait un AJAX bloquant qui attendait ~90s sans aucun
retour visuel autre qu'un spinner.

Nouveau flow:
- Backend: launcher.php lance update_firmware.sh en background
  (route update_firmware_start) et expose une route de polling
  incremental (update_firmware_progress) avec offset.
- Frontend: progress bar Bootstrap animee + label de l'etape en
  cours + timer mm:ss / estimation, plus streaming des logs
  toutes les 700ms.
- Sous-etape Step 3c (la plus longue): interpolation fine de la
  progression en comptant les 'Started X' (services demarres).
- Logs techniques masques par defaut dans <details>, ouverts
  automatiquement en cas d'echec pour faciliter le debug.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

html/launcher.php

@@ -418,7 +418,7 @@ if ($type == "update_firmware") {
     // Execute the comprehensive update script
     $command = 'sudo /var/www/nebuleair_pro_4g/update_firmware.sh 2>&1';
     $output = shell_exec($command);
-    
+
     // Return the output as JSON for better web display
     header('Content-Type: application/json');
     echo json_encode([
@@ -428,6 +428,71 @@ if ($type == "update_firmware") {
     ]);
 }
 
+// Start firmware update in background, returns immediately so the UI can poll progress.
+// Output is written to a temp log file. A 'done' marker file is created when finished.
+if ($type == "update_firmware_start") {
+    $logFile  = '/tmp/nebuleair_firmware_update.log';
+    $doneFile = '/tmp/nebuleair_firmware_update.done';
+
+    // Reset previous run markers
+    @file_put_contents($logFile, '');
+    @unlink($doneFile);
+
+    // Launch in background:
+    // - run the update script, capture stdout/stderr into log
+    // - append "EXIT_CODE=N" so the UI can detect success/failure
+    // - touch the done file so the UI knows the run finished
+    // - detach all stdio from PHP so this call returns immediately
+    $cmd = '(sudo /var/www/nebuleair_pro_4g/update_firmware.sh > '
+         . escapeshellarg($logFile) . ' 2>&1; '
+         . 'echo "EXIT_CODE=$?" >> ' . escapeshellarg($logFile) . '; '
+         . 'touch ' . escapeshellarg($doneFile) . ') > /dev/null 2>&1 &';
+    shell_exec($cmd);
+
+    header('Content-Type: application/json');
+    echo json_encode([
+        'success' => true,
+        'started_at' => time(),
+        'log_file' => $logFile
+    ]);
+    exit;
+}
+
+// Poll firmware update progress. The UI sends the byte offset it has already read,
+// we return any new content since that offset and whether the run has finished.
+if ($type == "update_firmware_progress") {
+    $logFile  = '/tmp/nebuleair_firmware_update.log';
+    $doneFile = '/tmp/nebuleair_firmware_update.done';
+
+    $offset = isset($_GET['offset']) ? (int)$_GET['offset'] : 0;
+
+    $content   = '';
+    $newOffset = $offset;
+    if (file_exists($logFile)) {
+        $size = filesize($logFile);
+        if ($size > $offset) {
+            $fp = fopen($logFile, 'r');
+            if ($fp) {
+                fseek($fp, $offset);
+                $content   = fread($fp, $size - $offset);
+                fclose($fp);
+            }
+            $newOffset = $size;
+        }
+    }
+
+    $done = file_exists($doneFile);
+
+    header('Content-Type: application/json');
+    echo json_encode([
+        'success' => true,
+        'content' => $content,
+        'offset'  => $newOffset,
+        'done'    => $done
+    ]);
+    exit;
+}
+
 if ($type == "upload_firmware") {
     // Firmware update via ZIP file upload (offline mode)
     if ($_SERVER['REQUEST_METHOD'] !== 'POST') {