fix: cantaloupe export subprocess cwd points to cantaloupe-downloader project

The subprocess.run for cantaloupe export was using cwd=admin_server_dir,
which meant 'python -m cantaloupe' couldn't find the local cantaloupe module.
Changed cwd to ~/projects/cantaloupe-downloader where the module lives.

Also added scripts/cantaloupe-sync.sh — the 6h cron job wrapper script.

cantaloupe_sync.py

@@ -419,10 +419,11 @@ async def run_sync(
         # Try subprocess call to cantaloupe export
         try:
             import subprocess
+            cantaloupe_dir = os.path.expanduser("~/projects/cantaloupe-downloader")
             result = subprocess.run(
                 ["python", "-m", "cantaloupe", "export", "--scheduled"],
                 capture_output=True, text=True, timeout=120,
-                cwd=str(Path(__file__).parent),
+                cwd=cantaloupe_dir,
             )
             if result.returncode != 0:
                 raise HTTPException(