Explicitly declare direct dep rather than rely on synapse

Author: ZenGround0

package.json

@@ -99,6 +99,7 @@
     "@helia/unixfs": "^6.0.1",
     "@ipld/car": "^5.4.2",
     "commander": "^14.0.1",
+    "ethers": "^6.15.0",
     "fastify": "^5.6.0",
     "helia": "^6.0.1",
     "it-to-buffer": "^4.0.10",