Usage ping: projectTemplates and projectStacks counts are swapped

### Current Behavior

In [forge/housekeeper/tasks/telemetryMetrics/004-platform.js#L41-L42](https://github.com/FlowFuse/flowfuse/blob/881e2595318cc9d174434308a2c95e21fa277112/forge/housekeeper/tasks/telemetryMetrics/004-platform.js#L41-L42) the two metrics are transposed:

- `platform.counts.projectTemplates` is computed from `ProjectStack.count()`
- `platform.counts.projectStacks` is computed from `ProjectTemplate.count()`

Every ping reports templates as stacks and stacks as templates.

### Expected Behavior

- `projectTemplates` counts `ProjectTemplate`
- `projectStacks` counts `ProjectStack`

### Steps To Reproduce

Code inspection, see link above.

### Environment

- FlowFuse version: main

Open forge/housekeeper/tasks/telemetryMetrics/004-platform.js at lines 41-42 and inspect how projectTemplates and projectStacks are assigned. Correct the model used for each count so templates use ProjectTemplate and stacks use ProjectStack, then verify the telemetry payload reports both metrics under the expected names.

Written by the indexing model from the issue text.