Clean up unused code and config

Remove PROCESSED_FILE references and update .env.example with placeholder
Uptime URLs for privacy.

Changes:
- Remove unused processed_file variable and loading in main.py
- Update .env.example to use generic Uptime URLs
- Remove processed_uids.txt from .gitignore

main.py

@@ -34,7 +34,6 @@ dest_pass = os.getenv("DEST_PASS")
 if not dest_pass:
     raise ValueError("DEST_PASS not set")
 folder = os.getenv("FOLDER", "INBOX")
-processed_file = os.getenv("PROCESSED_FILE", "processed_uids.txt")
 processed_msg_file = "processed_message_ids.txt"
 last_run_file = "last_run.txt"
 dry_run = os.getenv("DRY_RUN", "false").lower() == "true"