Fix bundled app failing to find Chromium browser

Set PLAYWRIGHT_BROWSERS_PATH to ~/Library/Caches/ms-playwright/ so the
PyInstaller .app uses the system-wide browser cache instead of looking
inside its own bundle.

stampli_core.py

@@ -1,9 +1,17 @@
 """Shared logic for Stampli bulk editor — used by both CLI scripts and the GUI."""
 
 import json
+import os
 import time
 from datetime import datetime, timedelta
 from pathlib import Path
+
+# Use system-wide Playwright browser cache so the bundled app doesn't
+# look for browsers inside its own .app bundle.
+_pw_cache = Path.home() / "Library" / "Caches" / "ms-playwright"
+if _pw_cache.is_dir():
+    os.environ.setdefault("PLAYWRIGHT_BROWSERS_PATH", str(_pw_cache))
+
 from playwright.sync_api import sync_playwright
 
 PROJECT_DIR = Path(__file__).parent