Initial scaffold: Flask webui + APScheduler + Playwright automation for MassPrice rule scheduling

Drives massprice.tcgplayer.com's Run Rule action per-rule on a
user-configured schedule (multiple times/day, day-of-week toggles),
replacing MassPrice's native scheduler (capped at 15 schedules
account-wide, one run/day, with observed clock drift). Deployed via
Forgejo push-to-deploy on Unraid, matching arr-summary/card-grader.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H6TgffxTvYhqxykAbVQg2v

storage.py

@@ -0,0 +1,35 @@
+"""Small JSON read/write helpers for the state files under DATA_DIR.
+
+Every file is written via a temp-file + os.replace so a crash mid-write
+never leaves a half-written JSON file behind for the next read.
+"""
+import json
+import os
+import threading
+
+DATA_DIR = os.environ.get("DATA_DIR", "/data")
+
+_lock = threading.Lock()
+
+
+def _path(name):
+    return os.path.join(DATA_DIR, name)
+
+
+def load(name, default):
+    path = _path(name)
+    with _lock:
+        if not os.path.exists(path):
+            return default
+        with open(path) as f:
+            return json.load(f)
+
+
+def save(name, data):
+    path = _path(name)
+    with _lock:
+        os.makedirs(DATA_DIR, exist_ok=True)
+        tmp = path + ".tmp"
+        with open(tmp, "w") as f:
+            json.dump(data, f, indent=2)
+        os.replace(tmp, path)