feat: add firmware versioning and device_type support (NebuleAir/ModuleAir)

- Add VERSION file (1.0.0) and changelog.json for firmware tracking
- Add device_type config param (nebuleair_pro default, backward compatible via INSERT OR IGNORE)
- Add device_type select in admin.html Protected Settings
- Add version badge and changelog modal in Updates section
- Add get_firmware_version and get_changelog PHP endpoints
- Display firmware version in update_firmware.sh after git pull

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

html/launcher.php

@@ -1515,6 +1515,47 @@ if ($type == "detect_envea_device") {
                                                                             |___/
 */
 
+// Get firmware version from VERSION file
+if ($type == "get_firmware_version") {
+    $versionFile = '/var/www/nebuleair_pro_4g/VERSION';
+    if (file_exists($versionFile)) {
+        $version = trim(file_get_contents($versionFile));
+        echo json_encode([
+            'success' => true,
+            'version' => $version
+        ]);
+    } else {
+        echo json_encode([
+            'success' => false,
+            'version' => 'unknown'
+        ]);
+    }
+}
+
+// Get changelog from changelog.json
+if ($type == "get_changelog") {
+    $changelogFile = '/var/www/nebuleair_pro_4g/changelog.json';
+    if (file_exists($changelogFile)) {
+        $changelog = json_decode(file_get_contents($changelogFile), true);
+        if ($changelog !== null) {
+            echo json_encode([
+                'success' => true,
+                'changelog' => $changelog
+            ]);
+        } else {
+            echo json_encode([
+                'success' => false,
+                'error' => 'Invalid changelog format'
+            ]);
+        }
+    } else {
+        echo json_encode([
+            'success' => false,
+            'error' => 'Changelog file not found'
+        ]);
+    }
+}
+
 // Get current CPU power mode
 if ($type == "get_cpu_power_mode") {
     try {