Provision the Telegram contact point, notification policy and message template from files and send one plain-text alert per distinct ERROR message

The chat id cannot be read by Grafana from the environment: it turns any value that looks like a number into
a number, quotes or not, and the Telegram integration then fails validation. The Grafana service now copies
the provisioning directory at start and substitutes @TELEGRAM_CHAT_ID@ in the contact point; the bot token
is still read with $__env. Both variables are required in compose.yaml and listed in .env.example.

The rule counts ERROR lines per service, environment and message (cut to 300 characters) over 5 minutes
and fires on the first one. The root policy groups by alertname, service and message, waits 30 seconds,
repeats after 4 hours and sends no resolve messages. The template prints service, environment, start time
in Asia/Tashkent, the message and the count. Rules and templates are not run through environment
substitution on Grafana 12.0, so their comments no longer ask for $$.