Fix path references in scripts after reorganization

Update 8 scripts to use Path(__file__).parent.parent as PROJECT_ROOT
so they resolve data/, output/, and internet_cables/ relative to the
project root rather than the caller's working directory.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/load_postgis_osm_data_centers.py

@@ -17,12 +17,15 @@ import json
 import os
 import sys
 import time
+from pathlib import Path
 from typing import Dict, List, Optional, Tuple
 
 import psycopg2
 import requests
 from psycopg2.extras import Json, execute_values
 
+PROJECT_ROOT = Path(__file__).parent.parent
+
 OVERPASS_URL = "https://overpass-api.de/api/interpreter"
 TABLE = "public.osm_data_centers"
 VIEW = "public.data_centers_union"
@@ -280,7 +283,7 @@ def parse_args() -> argparse.Namespace:
     parser = argparse.ArgumentParser(description=__doc__)
     parser.add_argument(
         "--cache-dir",
-        default="output",
+        default=str(PROJECT_ROOT / "output"),
         help="Directory to cache raw Overpass responses (default: output/).",
     )
     parser.add_argument(