Docs: Azure Blob Storage env vars differ between local emulator and deployed environments

## Is there an existing issue for this?

- [x] I have searched the existing issues

## Describe the bug

When using Azure Blob Storage with Aspire (`addAzureStorage` + `addBlobContainer`), the environment variables injected into the consuming app differ between local development (Azurite emulator) and deployed (Azure) environments, but this is not documented.

**Local (Azurite emulator):**
- `PLANTDATA_CONNECTIONSTRING` ✅ (full Azurite connection string)
- `PLANTDATA_URI` ❌ (not set)
- `PLANTDATA_BLOBCONTAINERNAME` ✅

**Deployed (Azure):**
- `PLANTDATA_CONNECTIONSTRING` ❌ (not set)
- `PLANTDATA_URI` ✅ (blob endpoint URI)
- `PLANTDATA_BLOBCONTAINERNAME` ✅

This means code that works locally with `PLANTDATA_CONNECTIONSTRING` breaks in production, and vice versa. The app needs to check for both and handle each case differently, but there's no documentation explaining this asymmetry.

## Expected Behavior

The docs for Azure Blob Storage integration should clearly document:
1. Which environment variables are injected in each environment (local vs deployed)
2. That `CONNECTIONSTRING` is only available with the emulator
3. The recommended pattern for writing code that works in both environments (e.g., check `URI` first, fall back to `CONNECTIONSTRING`)

## Steps To Reproduce

1. Create an Aspire app with `addAzureStorage('storage').runAsEmulator().addBlobContainer('plantdata')`
2. Reference the blob container from a Next.js/Node app
3. Note `PLANTDATA_CONNECTIONSTRING` works locally
4. Deploy to Azure — `PLANTDATA_CONNECTIONSTRING` is not set, only `PLANTDATA_URI`

## Aspire Version

Latest Aspire CLI + TypeScript AppHost (Node.js)

## Additional Context

Found during [#AspiriFridays](https://github.com/microsoft/aspire/labels/aspirifridays) stream while building a Next.js garden journal app. Our workaround is to check for `PLANTDATA_URI` first (production) and fall back to `PLANTDATA_CONNECTIONSTRING` (local), using `DefaultAzureCredential` for the URI path and `BlobServiceClient.fromConnectionString()` for the connection string path.