refactor: minor TigerStyle cleanups

- export_serving.py: move `import re` to module level — was imported
  inside a loop body on every iteration
- sitemap.py: add comment documenting that the in-memory TTL cache is
  process-local (valid for single-worker deployment, Dockerfile --workers 1)
- playtomic_availability.py: use `or "10"` fallback for
  CIRCUIT_BREAKER_THRESHOLD env var to handle empty-string case

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

extract/padelnomics_extract/src/padelnomics_extract/playtomic_availability.py

@@ -42,7 +42,7 @@ MAX_VENUES_PER_RUN = 20_000
 MAX_RETRIES_PER_VENUE = 2
 MAX_WORKERS = int(os.environ.get("EXTRACT_WORKERS", "1"))
 RECHECK_WINDOW_MINUTES = int(os.environ.get("RECHECK_WINDOW_MINUTES", "90"))
-CIRCUIT_BREAKER_THRESHOLD = int(os.environ.get("CIRCUIT_BREAKER_THRESHOLD", "10"))
+CIRCUIT_BREAKER_THRESHOLD = int(os.environ.get("CIRCUIT_BREAKER_THRESHOLD") or "10")
 
 # Parallel mode submits futures in batches so the circuit breaker can stop
 # new submissions after it opens. Already-inflight futures in the current