revert: use debug log for unselectable folders instead of warning

src/email_client.py

@@ -136,8 +136,9 @@ def fetch_unseen_emails(account: EmailAccount, skip_uids: set[bytes] | None = No
     skipped = 0
     for folder in folders:
         try:
-            status, _ = conn.select('"' + folder + '"', readonly=True)
+            status, _ = conn.select(folder, readonly=True)
             if status != "OK":
+                logger.debug("无法选择文件夹: %s", folder)
                 continue
             _, data = conn.uid("SEARCH", None, "UNSEEN")
             uids = data[0].split() if data[0] else []