Add optional status field to plugin_library.json schema

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The InfluxDB 3 Explorer UI needs a way to indicate plugin maturity levels (beta, deprecated) to users browsing the plugin library.

Currently there's no mechanism for plugin authors to signal that a plugin is in beta or experimental status. Users have no visibility into which plugins are production-ready vs. still in development.

**Requested capability:** Allow plugin entries in `plugin_library.json` to specify a status that the UI can display as a badge.

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## Suggested Implementation

Add an optional `status` field to plugin entries:

```json
{
"name": "Example Plugin",
"path": "influxdata/example/example.py",
"status": "beta",
...
}
```

**Field details:**
- **Name:** `status`
- **Type:** string (optional)
- **Values:** `"beta"` initially; Other values can be added later.
- **Default behavior:** If omitted, plugin is treated as stable/production (no badge shown)

**Backward compatibility:** Fully compatible - existing plugins without the field continue to work unchanged.

**UI behavior:** The Explorer UI will display a colored badge (e.g., orange "Beta" pill) on plugin cards for plugins with a status set.

Locate the plugin_library.json schema and inspect how plugin entries are validated and consumed by the InfluxDB 3 Explorer UI. Add an optional string status accepting beta, preserve the existing behavior when it is omitted, and verify that the UI can display the status as a badge.

Written by the indexing model from the issue text.