Support aspire secret set for deployment environments

## Summary

`aspire secret set` currently behaves as a local/development convenience, but deployment scenarios need a way to provide the same AppHost configuration/secret values for non-development environments.

## Problem

When deploying an Aspire app, especially a TypeScript AppHost or a non-interactive CI/local deployment, values set with `aspire secret set` are not a reliable deployment parameter mechanism. Agents and users have to switch to environment variables such as `Azure__SubscriptionId`, `Azure__Location`, `Azure__ResourceGroup`, and `Parameters__*` on the `aspire deploy` process.

That works, but it creates a gap:

- `aspire secret set` looks like the natural command for setting AppHost values.
- The values are only useful for local/dev behavior today.
- Deployment/non-interactive flows need separate environment-variable plumbing.
- It is not obvious when a value should be set with `aspire secret set` vs passed to `aspire deploy` as environment variables.

## Example scenario

A TypeScript AppHost deployment to Azure App Service needs deployment settings and parameters before running:

```bash
Azure__SubscriptionId="" \
Azure__Location="westus2" \
Azure__ResourceGroup="my-app-rg" \
Parameters__api_key="" \
aspire deploy --apphost ./apphost.ts --environment Production --non-interactive
```

Using `aspire secret set` for these values appears successful, but does not provide a complete deployment/environment-specific secret story.

## Desired outcome

Aspire should support setting AppHost secrets/configuration for deployment environments, not just local development. Ideally users could set values for an environment in a first-class way and have `aspire deploy --environment ` resolve them without requiring ad hoc process environment variables.

Possible shape to explore:

```bash
aspire secret set --environment Production "Parameters:api_key" ""
aspire secret set --environment Production "Azure:SubscriptionId" ""
```

The exact command shape is open, but the key requirement is that deployment environments have a clear, first-class way to store and resolve deployment secrets/configuration.

Start with the `aspire secret set` and `aspire deploy --environment` command flows, including non-interactive deployment and the TypeScript AppHost scenario. Define how environment-scoped values such as `Azure:SubscriptionId` and `Parameters:api_key` are stored and resolved, then verify that deployment no longer requires ad hoc process environment variables.

Written by the indexing model from the issue text.