Preserve links from other depts during filtered scans

clear_links() now only runs on full scans (dept=None). Dept-filtered
scans upsert without wiping, so GW links survive a Scan ELEC run
and vice versa.

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

scanner.py

@@ -62,7 +62,8 @@ def run_scan(dept: str = None, workers: int = 5, login_delay: int = 3):
     })
 
     scan_id = log_scan_start()
-    clear_links()  # Fresh start for links each scan
+    if dept is None:
+        clear_links()  # Full scan only — dept scans upsert without wiping other depts
 
     def on_progress(done, total, ip, result):
         from datetime import datetime