fix(site-explorer): skip machine ID generation for switches (dsx-ai-factory#4337)

Switches have their own `SwitchId` generation path and may not expose a
system serial number. Attempting to generate a `MachineId` for them
therefore produces misleading errors even when switch discovery
succeeds.

Skip `MachineId` generation for switches while preserving their
remaining enrichment and `SwitchId` generation.

## Related issues

Related to dsx-ai-factory#4277

## Type of Change
- [ ] **Add** - New feature or capability
- [ ] **Change** - Changes in existing functionality
- [x] **Fix** - Bug fixes
- [ ] **Remove** - Removed features or deprecated functionality
- [ ] **Internal** - Internal changes (refactoring, tests, docs, etc.)

## Breaking Changes
- [ ] **This PR contains breaking changes**

## Testing
- [ ] Unit tests added/updated
- [ ] Integration tests added/updated
- [x] Manual testing performed
- [ ] No testing required (docs, internal refactor, etc.)

## Additional Notes

Author: poroh

crates/site-explorer/src/lib.rs

@@ -169,7 +169,9 @@ pub fn enrich_endpoint_exploration_report(
     fw_config_snapshot: &FirmwareConfigSnapshot,
 ) {
     if !report.is_power_shelf() {
-        if let Err(error) = report.generate_machine_id(false) {
+        if !report.is_switch()
+            && let Err(error) = report.generate_machine_id(false)
+        {
             tracing::error!(%error, "Can not generate MachineId for explored endpoint");
         }
         report.model = report.model();