Improve documentation

Old issue snippets preserved for documentation purposes:

### https://github.com/datachain-ai/platform/issues/2501

> I made up a weird hybrid between the [documentation](https://dvc.org/doc/studio/self-hosting/installation/aws-ami#installation) and [iterative/helm-charts@dc56bf6/README.md](https://github.com/iterative/helm-charts/blob/dc56bf6afa34ce52b63507171b8f97c17c515db6/README.md?plain=1#L144-L168) in real time during [a customer] call. 🙈
>
> #### Consolidated version
>
> ```console
> $ helm repo update iterative
> $ helm upgrade --install --atomic --namespace studio --values values.yaml studio iterative/studio
> ```
>
> > [!NOTE]
> > I believe `helm repo add iterative https://helm.iterative.ai` shouldn't be necessary, but it looked like they didn't have the repository locally. 🤯

### https://github.com/datachain-ai/platform/issues/1881

> Studio Self-hosted: Document Git repo updates not reflected in Studio on dvc.org
> Webhook troubleshooting

### https://github.com/datachain-ai/platform/issues/1362

> One customer experienced a rare issue where the K3s node was marked `NotReady`.
>
> Running `kubectl uncordon ` fixed the problem.
>
> We need to add this to the troubleshooting section on dvc.org