fix(studio): show service role key in ConnectSheet for projects using legacy keys (#50516)

## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.

YES

## What kind of change does this PR introduce?

Bug fix #50515

## What is the new behavior?

ConnectSheet now falls back to the legacy `service_role` key for
projects using legacy JWT keys.



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Improved secret-key resolution by falling back to the service key when
a secret key is unavailable.
* Prevented attempts to reveal a secret when no secret key identifier
exists.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/studio/components/interfaces/ConnectSheet/useConnectServerEnv.ts

@@ -69,7 +69,7 @@ export function useConnectServerEnv(): UseConnectServerEnvResult {
     { enabled: canReadAPIKeys }
   )
   const publishableKey = keys?.publishableKey?.api_key ?? keys?.anonKey?.api_key ?? ''
-  const secretKey = keys?.secretKey
+  const secretKey = keys?.secretKey ?? keys?.serviceKey
   const maskedValue = secretKey?.api_key
     ? `${secretKey.api_key.slice(0, 15)}${SECRET_MASK}`
     : 'your-secret-key'
@@ -79,7 +79,7 @@ export function useConnectServerEnv(): UseConnectServerEnvResult {
     isLoading: isRevealing,
     reveal,
     clear,
-  } = useRevealedSecret({ projectRef, id: secretKey?.id })
+  } = useRevealedSecret({ projectRef, id: secretKey?.id ?? undefined })
 
   // toggle() and getSecretValue() can both decide to reveal before either
   // resolves (e.g. clicking "Reveal" and "Copy" in quick succession); share