Drop enrichment_attempts default after backfill

Columns must not carry DEFAULT clauses. The DEFAULT only backfills
existing rows when the non-nullable column is added, so drop it in the
same migration; inserts already supply enrichment_attempts explicitly.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/coredata/migrations/20260609T120000Z.sql

@@ -21,6 +21,13 @@ ADD
 ADD
     COLUMN enrichment_attempts INTEGER NOT NULL DEFAULT 0;
 
+-- The DEFAULT only backfills existing rows; drop it so inserts must
+-- supply the value explicitly.
+ALTER TABLE
+    common_third_parties
+ALTER COLUMN
+    enrichment_attempts DROP DEFAULT;
+
 -- Partial index backs the enrichment worker's claim query, which polls
 -- only rows currently queued for enrichment.
 CREATE INDEX common_third_parties_enrichment_requested_at_idx