Refactor authentication logic in fetch.ts

[iKausik]

What kind of change does this PR introduce?

• 🛠 Refactor (Code improvement without changing functionality)

What is the current behavior?

• fetch.ts currently sets accessToken using a nullish coalescing (??) fallback.

• This can lead to unintended behavior where supabaseKey is assigned if getAccessToken() returns undefined or null.

Before (Current behavior):

const accessToken = (await getAccessToken()) ?? supabaseKey;

if (!headers.has('Authorization')) {
      headers.set('Authorization', `Bearer ${accessToken}`)
    }

What is the new behavior?

• The refactored code separates token retrieval from fallback logic.

• Now, authentication headers are set only if accessToken exists.

• This improves clarity and avoids accidental assignment of Authorization: Bearer undefined.

After (Refactored behavior):

const accessToken = await getAccessToken()

if (accessToken && !headers.has('Authorization')) {
      headers.set('Authorization', `Bearer ${accessToken}`)
    }

Additional context

• This change improves readability without altering core functionality.

• No breaking changes expected.

• Code remains compatible with the existing authentication flow.