Move metadata xlsx/TSV to /mnt/data/projects/cupido/

Consolidates everything bulky (tracking DBs, targets, metadata
spreadsheet) under a single DATA_VOLUME root outside the ownCloud-synced
repo. Notebooks now use a visible DATA_DIR = Path(...) idiom rather than
walking up the filesystem with PROJECT_ROOT.parent — easier for students
with no Python background to follow.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/export_video_db_index.py

@@ -26,7 +26,7 @@ from pathlib import Path
 
 import pandas as pd
 
-from config import INVENTORY_CSV, TRACKING_OUTPUT_DIR, VIDEO_INFO_XLSX
+from config import INVENTORY_CSV, TRACKING_OUTPUT_DIR, VIDEO_INFO_TSV, VIDEO_INFO_XLSX
 
 
 _TIME_RE = re.compile(r"^(\d{8})_(\d{1,2})(\d{2})?(AM|PM)$", re.IGNORECASE)
@@ -138,7 +138,7 @@ def main() -> None:
     parser.add_argument(
         "--out",
         type=Path,
-        default=VIDEO_INFO_XLSX.with_suffix(".tsv"),
+        default=VIDEO_INFO_TSV,
         help="output TSV path (default: alongside the xlsx)",
     )
     args = parser.parse_args()