fix: correct hash schema and stream hashing

packages/db/migrations/0007_asset_hashes.sql

@@ -1,12 +1,9 @@
 CREATE TABLE IF NOT EXISTS asset_hashes (
-  id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
-  asset_id uuid NOT NULL REFERENCES assets(id) ON DELETE CASCADE,
+  asset_id uuid PRIMARY KEY REFERENCES assets(id) ON DELETE CASCADE,
   bucket text NOT NULL,
   sha256 text NOT NULL,
   created_at timestamptz NOT NULL DEFAULT now()
 );
 
-CREATE INDEX IF NOT EXISTS asset_hashes_asset_id_idx ON asset_hashes(asset_id);
-
 CREATE UNIQUE INDEX IF NOT EXISTS asset_hashes_bucket_sha256_idx
 ON asset_hashes(bucket, sha256) WHERE sha256 IS NOT NULL;