Restore: login retry, skip processed scans, no-retry on 404, started_at tracking

Co-authored-by: Cursor <cursoragent@cursor.com>

spruce/session.py

@@ -14,6 +14,7 @@ from bs4 import BeautifulSoup
 
 from spruce.download_result import (
     OK,
+    PERMANENT_MISSING,
     UNKNOWN,
     DownloadResult,
     classify_http_error,
@@ -263,6 +264,10 @@ class MachineSession:
                     and exc.response is not None
                 ):
                     sc = exc.response.status_code
+                cl = classify_http_error(sc, exc)
+                if cl == PERMANENT_MISSING:
+                    # 404/410 will never succeed — don't waste time retrying.
+                    return DownloadResult(0, sc, str(exc), cl)
                 if attempt < retries:
                     log.warning(
                         "Attempt %d/%d failed %s: %s — retrying in %.0fs",
@@ -281,7 +286,6 @@ class MachineSession:
                         url,
                         exc,
                     )
-                    cl = classify_http_error(sc, exc)
                     return DownloadResult(0, sc, str(exc), cl)
         return DownloadResult(0, None, "download_file: exhausted", UNKNOWN)