feat: add POST /api/action/sync-time endpoint for manual NTP/RTC sync

Allows triggering NTP sync + hardware RTC write from the web UI,
useful for periodic manual time correction (e.g., every 30 days
or when charging).

Co-authored-by: Cursor <cursoragent@cursor.com>

src/web_server.cpp

@@ -183,6 +183,12 @@ void AppWebServer::setupAPIRoutes() {
             req->send(200, "application/json", response);
         });
 
+    _server.on("/api/action/sync-time", HTTP_POST,
+        [this](AsyncWebServerRequest* req) {
+            _wifi->syncNTP();
+            req->send(200, "application/json", "{\"ok\":true,\"msg\":\"RTC synced\"}");
+        });
+
     _server.on("/api/action/reboot", HTTP_POST,
         [](AsyncWebServerRequest* req) {
             req->send(200, "application/json", "{\"ok\":true,\"msg\":\"Rebooting...\"}");