Fix Stop button not halting Google Workspace scan

Two bugs in the abort mechanism:

1. POST /api/scan/stop only set state._scan_abort (M365/file abort event)
   but never touched state._google_scan_abort. Now sets both.

2. _check_abort() inside _run_google_scan imported gdpr_scanner._scan_abort
   (= state._scan_abort, the M365 event) instead of using the module-level
   _scan_abort alias (= state._google_scan_abort). This meant the dedicated
   /api/google/scan/cancel endpoint — which correctly sets _google_scan_abort
   — was silently ignored by the scan loop. Fixed to use the module-level
   alias consistently. Also aligned the end-of-scan checkpoint-clear check.

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

routes/scan.py

@@ -114,6 +114,7 @@ def scan_start():
 @bp.route("/api/scan/stop", methods=["POST"])
 def scan_stop():
     state._scan_abort.set()
+    state._google_scan_abort.set()
     return jsonify({"status": "stopping"})