🔧 telemetry: make CONNITO_TELEMETRY_PORT actually configurable

[george-connito]

CONNITO_TELEMETRY_PORT shipped in the validator image but was never read by any code — the exporter port was hardcoded to 8200 + rank. An operator whose host already had 8200 occupied would set the variable, see no effect, and end up with a validator that runs fine on chain while the exporter fails to bind ("Address already in use") and serves nothing. The failure is caught and logged, so the only symptom is silence. This is what took validator slot 5 off the dashboard.

Wiring the code alone would NOT have fixed it — three further pieces were needed, each of which would have reproduced the same "setting does nothing" bug on its own:

• run.py: new resolve_telemetry_port(rank, env). The var is a base port, not absolute: effective port is base + rank, preserving the semantics of the 8200 default it replaces so a multi-rank host stays collision-free (an absolute override would point every rank at one port and all but one would fail to bind — the very bug being fixed). Invalid input warns and falls back rather than raising: a typo in an operator's .env must not take a validator off chain over a telemetry setting.
• docker-compose.yml: pass CONNITO_TELEMETRY_PORT into the container. A value in .env only interpolates into the compose file; without an explicit environment: entry it never reaches the process.
• docker-compose.yml: healthcheck now follows the same variable, so overriding the port doesn't leave the container permanently unhealthy probing a port nothing binds.
• Dockerfile: comment now documents the real behaviour.

Also removes two decorations that were the same class of trap:

• CONNITO_DHT_PORT — deliberately NOT wired. The DHT port is already configured by dht.port in validator.yaml, and it is announced to peers; a second competing source of truth could make a validator advertise one port while listening on another, which is a worse failure than the one being fixed. Removed, with a comment pointing at the real knob.
• CONNITO_STATE_API_PORT + the 8300/tcp EXPOSE — the /v1/state.json API they referenced no longer exists.

Operators overriding the port must open the new port in their firewall.

Tests: 12 new covering default, rank offset, override-as-base, whitespace, non-numeric / out-of-range / float / hostile input fallbacks, and base+rank overflow. Verified in the stable image that the env var now takes effect end to end, and that docker compose config interpolates both the container env and the healthcheck for default and override.