Set GITHUB_TOKEN on Azure Container App for bingo dashboard

The bingo app dashboard (`/dashboard.html`) has a `/api/issues` endpoint that proxies GitHub Issues to display live gotchas and project submissions. It requires a `GITHUB_TOKEN` environment variable.

## Steps

1. Create a GitHub Personal Access Token (classic) with `repo` scope (or a fine-grained token with Issues read access to `equinor/learnathon`)
2. Set it as an environment variable on the Azure Container App running the bingo app:
```
az containerapp update --name --resource-group --set-env-vars GITHUB_TOKEN=
```
3. Verify: `curl https:///api/issues?label=gotcha` should return `[]` (empty array, not a 503)

## Optional

You can also set `GITHUB_REPO` env var if the repo isn't `equinor/learnathon` (that's the default).