Add Dependency Mapping Between Infrastructure and Uptime Apps

### Is your feature request related to a problem? Please describe.
Currently, the **Uptime** page monitors applications via HTTP requests (to check if an app is up or down), while the **Infrastructure** page monitors servers (Windows/Linux). These two views are separate.

The problem is:
- When an infrastructure host (e.g., "Infra A") goes down, there is no way to see which HTTP-based applications monitored under **Uptime** are affected.
- This makes it harder to quickly identify the impact of an infrastructure outage on dependent apps.

### Describe the solution you'd like
Add the ability to **link Uptime checks (apps monitored by HTTP) to Infrastructure hosts**.

Example workflow:
- In the Infrastructure page, when viewing "Infra A", I can associate it with "App A" and "App B" (which are already defined as HTTP checks in Uptime).
- If "Infra A" goes down, Checkmate can display that "App A" and "App B" are impacted (or potentially unreachable).

This provides a dependency mapping between infra and apps, helping users see the “blast radius” of an infra failure.

### Describe alternatives you've considered
- Naming conventions that try to link infra and app checks (doesn’t give real-time impact visibility).

### Additional context
This would:
- Give a holistic view of both infra and app health in one place.
- Help teams immediately know which applications are affected when an infra host goes down.

The issue names the Infrastructure and Uptime pages but no files, tests, or entry points. Start by locating those page implementations and the data used for infrastructure hosts and HTTP checks; define the association and outage-impact behavior, then verify that linked apps are shown when a host goes down.

Written by the indexing model from the issue text.