Retrieve object metadata (HEAD request) from R2 bucket.
Used by the upload complete endpoint to verify the actual stored byte size
against the 5 GB cap. Quota is enforced earlier, at presign time, via
incrementUsageIfAllowed in POST /api/uploads/presign.
Parameters
key: string
Object key in R2 bucket
Optionaloptions: {signal?:AbortSignal}
Returns Promise<number>
Actual size of the stored object in bytes (0 if ContentLength is absent)
Retrieve object metadata (HEAD request) from R2 bucket. Used by the upload complete endpoint to verify the actual stored byte size against the 5 GB cap. Quota is enforced earlier, at presign time, via incrementUsageIfAllowed in POST /api/uploads/presign.