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/cm-sandbox/src/spec.rs

@@ -30,3 +30,13 @@ pub struct ExecResult {
     pub stdout: String,
     pub stderr: String,
 }
+
+/// A sandbox the driver currently knows about (label-filtered), used by the
+/// reaper to find orphans — containers that outlived the process that made them.
+#[derive(Debug, Clone)]
+pub struct ManagedSandbox {
+    /// Engine container/pod id.
+    pub id: String,
+    /// Creation time, unix seconds (for TTL-based reaping).
+    pub created_unix: i64,
+}