Archive node is wasting effort inserting duplicated data into DB

[glyh]

When archive is in operation, it may insert duplicated data. While this is fine, because it doesn't know what state the DB is in, it's bad that it'll retry it even it should know the data exists.

Here's an example log line:

2025-11-14 07:39:13 UTC [Warn] Error when adding block data to the database, rolling back transaction: $error
  error: "Request to <postgres://postgres:_@postgres:5432/archive> failed: ERROR:  duplicate key value violates unique constraint \"snarked_ledger_hashes_pkey\"\nDETAIL:  Key (id)=(88912) already exists.\n. Query: \"INSERT INTO snarked_ledger_hashes (value) VALUES ($1) RETURNING id\"."
2025-11-14 07:39:13 UTC [Warn] Error in add_block_aux : $error. Retrying...
  error: "Request to <postgres://postgres:_@postgres:5432/archive> failed: ERROR:  duplicate key value violates unique constraint \"snarked_ledger_hashes_pkey\"\nDETAIL:  Key (id)=(88912) already exists.\n. Query: \"INSERT INTO snarked_ledger_hashes (value) VALUES ($1) RETURNING id\"."

We should ensure this scenario doesn't happen.