[Feature] Support agentless SSH monitoring using hostname / mDNS instead of static IP

### Feature Request

## **Feature Request**

### A concise description of the feature

Currently, when adding a Debian Linux node as an **agentless SSH monitor**, HertzBeat requires a **static IP address**.
I would like to request support for using **hostname-based resolution (DNS or mDNS, e.g. `node-name.local`)** instead of only IP-based configuration.

This would allow monitoring to continue seamlessly even when the node’s IP address changes.

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## **Is your feature request related to a problem? Please describe**

Yes.

In our environment:

* Debian Linux nodes are added as **agentless SSH clients**
* Some nodes receive **dynamic IPs via DHCP**
* When the IP changes, HertzBeat marks the node as **DOWN**, even though the machine is still online and reachable via hostname

This causes:

* False “node offline” alerts
* Manual reconfiguration whenever IPs change

Using **hostname or mDNS-based SSH monitoring** would solve this issue.

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## **Additional Context / Use Case**

* Environment: Debian Linux (agentless SSH)
* Monitoring type: OS / CPU / Memory / Disk
* Network: DHCP-based, IPs may change
* Hostnames are resolvable via:

* mDNS (`*.local`)
* or internal DNS

**Example use case:**

```text
node-01.local → IP changes → monitoring should continue without interruption
```
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### Is your feature request related to a problem? Please describe

## **Expected Behavior**

* Allow SSH monitoring configuration using:

* Hostname (DNS)
* mDNS hostname (`.local`)
* HertzBeat should resolve the hostname dynamically before each check
* Node should not be marked DOWN solely due to IP change

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## **Alternatives / Questions**

If this feature is not currently supported, guidance on **best practices** would also be very helpful, such as:

* Recommended DNS/DHCP setup
* Any workaround for dynamic IP environments

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## **Appreciation**

Thank you to the HertzBeat maintainers and contributors for building such a **powerful, clean, and user-friendly monitoring platform**.
It has been extremely useful for our production and edge environments 🙏

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### Describe the solution you'd like

_No response_

### Describe alternatives you've considered

_No response_

### Additional context

_No response_