Fix duplicate detection by ensuring folder selection

Call ensure_folder_exists before check_duplicate to select the dest
folder, allowing IMAP SEARCH to work in SELECTED state.

Changes:
- Move dest.ensure_folder_exists(folder) before check_duplicate in process_email
- Add logging to check_duplicate for debugging

email_forwarder/email_forwarder.py

@@ -106,8 +106,10 @@ class DestImap(ImapClient):
         """Check if Message-ID exists in current folder."""
         try:
             results = self._search(f'HEADER Message-ID "{msg_id}"')
+            logging.debug(f"Check duplicate for {msg_id}: found {len(results)} matches")
             return len(results) > 0
-        except:
+        except Exception as e:
+            logging.error(f"Error checking duplicate for {msg_id}: {e}")
             return False
 
     def _create_folder(self, folder: str):
@@ -205,6 +207,11 @@ class EmailForwarder:
                     continue
                 if msg_id in self.processed_ids:
                     continue
+                self.dest.ensure_folder_exists(folder)
+                if self.dest.check_duplicate(msg_id):
+                    continue
+                if msg_id in self.processed_ids:
+                    continue
                 if self.dest.check_duplicate(msg_id):
                     continue