Fix API calls by all workers

Quite a complex commit by GPT. I'll rewrite it somewhen

blueprints/risdeveau/modules/api/shared_cache.py

@@ -0,0 +1,53 @@
+from __future__ import annotations
+
+import json
+import os
+import tempfile
+from typing import Any, Optional, Tuple
+
+
+def cache_dir() -> str:
+    """Directory where the scheduler owner writes shared cache JSON files."""
+    d = os.environ.get("LAIR_CACHE_DIR", "/tmp/lair-cache")
+    os.makedirs(d, exist_ok=True)
+    return d
+
+
+def cache_file(name: str) -> str:
+    return os.path.join(cache_dir(), f"{name}.json")
+
+
+def atomic_write_json(path: str, payload: dict) -> None:
+    """Write JSON atomically so readers never observe partial content."""
+    parent = os.path.dirname(path) or "."
+    fd, tmp = tempfile.mkstemp(prefix=".tmp-", dir=parent)
+    try:
+        with os.fdopen(fd, "w", encoding="utf-8") as f:
+            json.dump(payload, f, ensure_ascii=False, separators=(",", ":"))
+        os.replace(tmp, path)
+    finally:
+        try:
+            if os.path.exists(tmp):
+                os.unlink(tmp)
+        except Exception:
+            pass
+
+
+def load_json_if_newer(path: str, last_mtime: float) -> Tuple[Optional[dict], float]:
+    """Load JSON only if the file exists and has mtime newer than last_mtime."""
+    try:
+        st = os.stat(path)
+    except FileNotFoundError:
+        return None, last_mtime
+    except Exception:
+        return None, last_mtime
+
+    mtime = float(st.st_mtime)
+    if mtime <= float(last_mtime):
+        return None, last_mtime
+
+    try:
+        with open(path, "r", encoding="utf-8") as f:
+            return json.load(f), mtime
+    except Exception:
+        return None, last_mtime