refactor: extract atomic JSON helpers to io_utils

Centralize read_json/write_json_atomic used by pipeline meta I/O and
worker processed.json bookkeeping. Preserves corrupt-file warning in
load_processed().

Co-authored-by: Cursor <cursoragent@cursor.com>

app/worker.py

@@ -13,7 +13,6 @@ pipeline is CPU heavy (gmic/rembg) and the worker container is capped at
 
 from __future__ import annotations
 
-import json
 import logging
 import shutil
 import time
@@ -21,11 +20,10 @@ from pathlib import Path
 from typing import Any
 
 from . import config, pipeline
+from .io_utils import read_json, write_json_atomic
+from .logging_config import configure_logging
 
-logging.basicConfig(
-    level=logging.INFO,
-    format="%(asctime)s %(levelname)s [%(name)s] %(message)s",
-)
+configure_logging()
 logger = logging.getLogger("livef12.worker")
 
 
@@ -42,17 +40,15 @@ def ensure_dirs() -> None:
 def load_processed() -> dict[str, Any]:
     if not config.PROCESSED_FILE.exists():
         return {}
-    try:
-        return json.loads(config.PROCESSED_FILE.read_text(encoding="utf-8"))
-    except (OSError, ValueError):
-        logger.warning("processed.json unreadable, starting fresh")
-        return {}
+    data = read_json(config.PROCESSED_FILE)
+    if isinstance(data, dict):
+        return data
+    logger.warning("processed.json unreadable, starting fresh")
+    return {}
 
 
 def save_processed(processed: dict[str, Any]) -> None:
-    tmp = config.PROCESSED_FILE.with_suffix(".json.tmp")
-    tmp.write_text(json.dumps(processed, indent=2, ensure_ascii=False), encoding="utf-8")
-    tmp.replace(config.PROCESSED_FILE)
+    write_json_atomic(config.PROCESSED_FILE, processed)
 
 
 def _file_key(path: Path) -> str: