Adds a new global `vector-networks` property on the logs plugin that takes a comma-separated list of Docker networks. When set, the rendered compose file declares each network plus `bridge` as external and joins them on the vector service, so `docker compose up` reconciles attachments on every `logs:vector-start`. When unset, the existing `network_mode: bridge` template is preserved unchanged. The value is validated against `docker network inspect` at set time, rejects the reserved `bridge` entry, and is surfaced in `dokku logs:report` via `--logs-vector-global-networks`.
If a global vector-sink property on the logs plugin is set, we will use that to configure a log sink (defaulting to console output otherwise). Note that the actual configuration still needs to be a valid DSN representing a Vector log sink.
While this does not support pinning log sinks to specific apps, it opens up integration for those who use a single k3s cluster in shared tenancy.
