Add button docs to eurotronic_cometblue (home-assistant#44759)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: rikroe

source/_integrations/eurotronic_cometblue.markdown

@@ -2,6 +2,7 @@
 title: Eurotronic Comet Blue Thermostats
 description: Instructions on how to integrate Eurotronic Comet Blue Thermostats into Home Assistant.
 ha_category:
+  - Button
   - Climate
 ha_iot_class: Local Polling
 ha_release: 2026.5
@@ -13,6 +14,7 @@ ha_domain: eurotronic_cometblue
 ha_integration_type: device
 ha_quality_scale: bronze
 ha_platforms:
+  - button
   - climate
 ---
 
@@ -71,6 +73,10 @@ Additionally, the following modes are available:
 - **Heat**: Valve is fully open.
 - **Auto**: The thermostat controls the temperature automatically, based on the target temperature.
 
+### Button
+
+The integration provides a **Sync time** button for each device. Pressing this button synchronizes the thermostat's internal clock with Home Assistant's current time.
+
 ## Data updates
 
 The integration {% term polling polls %} data from the thermostat every 5 minutes by default.