Fix f-string lint and formatting in backfill scripts

Drop the f prefix from two f-strings that carry no placeholders
(F541) and apply ruff format, so `ruff check` / `ruff format --check`
pass in CI.

scripts/backfill_sites.py

@@ -8,7 +8,9 @@ Usage:
 import sys
 import os
 
-sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "lambdas", "po", "site_extractor"))
+sys.path.insert(
+    0, os.path.join(os.path.dirname(__file__), "..", "lambdas", "po", "site_extractor")
+)
 
 import boto3
 from handler import extract_site_code, parse_address, upsert_site
@@ -65,7 +67,7 @@ def main():
         if extracted % 100 == 0:
             print(f"  Processed {extracted} POs with site codes...")
 
-    print(f"\nBackfill complete:")
+    print("\nBackfill complete:")
     print(f"  Total POs scanned: {len(pos)}")
     print(f"  POs with site code: {extracted}")
     print(f"  POs without site code: {skipped}")

scripts/reprocess.py

@@ -48,7 +48,11 @@ def build_s3_event(bucket: str, key: str) -> dict:
 
 def main():
     parser = argparse.ArgumentParser(description="Reprocess missed PO emails")
-    parser.add_argument("--execute", action="store_true", help="Actually invoke the Lambda (default is dry-run)")
+    parser.add_argument(
+        "--execute",
+        action="store_true",
+        help="Actually invoke the Lambda (default is dry-run)",
+    )
     args = parser.parse_args()
 
     bucket = get_bucket_name()
@@ -73,7 +77,7 @@ def main():
             print(f"  [dry-run] {key}")
 
     if not args.execute:
-        print(f"\nDry run complete. Re-run with --execute to invoke the Lambda.")
+        print("\nDry run complete. Re-run with --execute to invoke the Lambda.")
 
 
 if __name__ == "__main__":