feat: request time-boxed operation access from the CLI (#540)

## Summary
- Adds `alien access-requests create/get/wait` so CLI/API callers
(customers running their own AI agent, or a human) can request
time-boxed operation access without Slack.
- `create` supports both exact (`--operation <plugin>/<operation>`) and
wildcard (`--operation <plugin>/*` + `--max-risk`) requests through a
single `--operation` flag.
- `get`/`wait` fetch and print the customer's actual `kubectl patch ...`
approve command once the operator materializes the grant CR, polling
briefly so it's available right after creation rather than requiring a
follow-up call.
- `operations invoke --request-access` creates an access request, waits
for approval, then re-invokes the operation.
- Approval always happens on the customer's side, in-cluster — there is
deliberately no CLI action that approves a request.

## Test plan
- [x] `cargo check -p alien-cli` and `cargo test -p alien-cli --lib
access_requests` pass
- [x] Manually exercised end-to-end against a local kind cluster: create
→ operator materializes grant CR → `kubectl patch` approve →
`wait`/`invoke` dispatches → verified pod restart via `kubectl get pods`
- [x] Manually exercised the wildcard path (`--operation 'kubernetes/*'
--max-risk mutating`)

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Author: ab-alien-dev