Containerize the telemetry ingest service and reorganize source layout. Added misc/data/Dockerfile with a multi-stage build (golang:1.23-alpine -> alpine:3.23) to produce /app/telemetry-ingest, run as a non-root user, expose :8080, and provide default env vars for configuration (LISTEN_ADDR, MAX_BODY_BYTES, RATE_LIMIT_RPM, RATE_BURST, RATE_KEY_MODE, ENABLE_REQUEST_LOGGING, UPSTREAM_TIMEOUT_MS). Renamed misc/ingest.go to misc/data/service.go to reflect the new directory structure.
