Reaping: sandbox orphan reaper + DB expiry/retention sweeper + volume-init retry

Closes the cleanup gaps found in review (latent today; bites under load/crashes).

Sandbox containers (cm-sandbox / cm-runtime):
- label every sandbox `clawmates.sandbox={agent|browser}` at create
- SandboxDriver::list_managed(kind) (Docker label filter + K8s label selector)
- SandboxManager::reconcile_orphans(ttl) + spawn_reaper: removes engine
  containers no live handle owns (ZERO = all)
- boot reconciliation (every pre-existing sandbox is an orphan from a dead
  process) + periodic reaper (5m interval / 10m TTL)
- SIGTERM graceful drain: serve().with_graceful_shutdown → shutdown() both
  managers so a redeploy can't leak; destroy errors now logged not swallowed

DB expiry/retention (cm-db cleanup.rs + cm-api cleanup_sweeper, hourly):
- expire auth_sessions + oauth_states past expires_at (security)
- prune sent outbox(7d), run_events(14d), routine_runs(30d), terminal
  topology_runs(90d), consumed execution_grants(7d)

Compose: volume-init restart "no" → on-failure:5 (retry instead of wedging boot).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

crates/bins/clawmates-server/Cargo.toml

@@ -22,7 +22,7 @@ cm-sandbox = { path = "../../cm-sandbox" }
 cm-scheduler = { path = "../../cm-scheduler" }
 cm-domain = { path = "../../cm-domain" }
 time = { workspace = true }
-tokio = { workspace = true }
+tokio = { workspace = true, features = ["signal"] }
 
 [lints]
 workspace = true