Only use a proxy for tgapp when mykeys['proxy'] is explicitly configured, avoiding the dead default local proxy and restoring Telegram polling startup.
Closes#175
The proxy was hardcoded to http://127.0.0.1:2082 which breaks for users
without a local proxy (e.g. international users with direct access).
Now defaults to None; users who need a proxy can set it in mykey.py.
