## Why

The deletion engine already exposes a one-shot `buzz-admin deletions
drain` command, but operators have no safe way to schedule it. A generic
workload wrapper could expose arbitrary commands or inherit relay
credentials, which would add a second control plane and widen the blast
radius.

## What

This PR adds an opt-in Kubernetes CronJob for the typed deletion drain
command. It is stacked on #7818, which adds owner-request admission.

## How

The chart keeps the job disabled by default. The CronJob uses `Forbid`,
zero Kubernetes retries, bounded runtime and history, and only the
database, Redis, and object-store settings required by the executor.
PostgreSQL leases, checkpoints, and retry timing remain the sole durable
retry authority.

The closed `_operator-jobs.tpl` helper centralizes safe CronJob
mechanics without creating an arbitrary command or environment registry.
This leaves the touched system simpler than a general job framework
would.

## Risk

The deployment blast radius is low because the job is disabled by
default. When enabled, it can run destructive deletion work that the
database has already approved, so the chart limits concurrency, retries,
credentials, and execution time.

## Testing

Rendered every `deploy/charts/buzz/ci/*.yaml` fixture with `helm
template`; all passed at `e68cb753bb6673aa1baa60046969bdb2d4738b62`.

Ran the full independent Desktop, Tauri, and web lanes; all passed at
`e68cb753bb6673aa1baa60046969bdb2d4738b62`. Flutter package resolution
made no progress within three minutes, so the mobile lane is not claimed
green.

## Bigger picture

A later stack layer must inventory and approve admitted owner requests.
Until then, this scheduler cannot make a new owner request destructive.

Generated with Codex

---------

Signed-off-by: tornquist <tornquist@squareup.com>
Signed-off-by: Codex <noreply@openai.com>
Signed-off-by: Elrond <28d6302a099e5225b02c4155ac4236e4912603df2ab08dbfc2f4fef08ce598c8@buzz.block.builderlab.xyz>
Co-authored-by: Codex <noreply@openai.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
Co-authored-by: Elrond <28d6302a099e5225b02c4155ac4236e4912603df2ab08dbfc2f4fef08ce598c8@buzz.block.builderlab.xyz>