STEP 1: GET URL
Send a POST request to get a secure upload URL.
| Parameter | Type | Required? | Description |
|---|---|---|---|
| filename | String | Yes | Original filename, e.g., "spaceship.png" |
| expire | String | No | Expiration. "never", "1", "7", "30" |
STEP 2: UPLOAD FILE
Send a PUT request with binary file data to the `signedUrl` from Step 1.