chore: gitignore hosts_*.json files (#1343)

## Motivation

`hosts_*.json` files are local host configuration snapshots that
shouldn't be tracked in version control.

## Changes

Added `hosts_*.json` pattern to `.gitignore`.

## Why It Works

The glob pattern `hosts_*.json` matches any file starting with `hosts_`
and ending with `.json` in the repo root.

## Test Plan

### Manual Testing
- Verified that `hosts_*.json` files are ignored by git after this
change.

### Automated Testing
- No automated tests needed for a `.gitignore` change.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -28,3 +28,6 @@ target/
 dashboard/build/
 dashboard/node_modules/
 dashboard/.svelte-kit/
+
+# host config snapshots
+hosts_*.json