refactor(config.example.yaml): rename uint64_to_string_fields to bigint_to_string_fields

feat(config.example.yaml): add peer_id_unique_key to bigint_to_string_fields list

Author: mattevans

config.example.yaml

@@ -45,8 +45,9 @@ api:
   # Exclude tables matching these patterns from API exposure
   exclude:
     - "*_local"
-  # NEW: Field whitelist for uint64→string conversion
-  uint64_to_string_fields:
+  # Field whitelist for uint64→string conversion
+  bigint_to_string_fields:
+    - peer_id_unique_key
     - consensus_payload_value
     - execution_payload_value
     - block_number