Epic: CLI telemetry in the backend

[khvn26]

Emit a structured event for Flagsmith CLI API usage, route it to Amplitude for retention analysis, and to InfluxDB for volume and error-rate graphs.

Event

cli.request.made, emitted once per authenticated CLI request:

cli.version        e.g. "2.0.0-beta.3", "dev"
cli.os             e.g. "darwin"
cli.arch           e.g. "arm64"
organisation.id    int, or absent when it cannot be resolved unambiguously
status             "success" | "error", from response.status_code >= 400
amplitude.user_id  str(request.user.uuid), or absent for a master API key