feat(daemon): policy apply via pam-auth-update + lockout simulator (Phase 4+5)

Lands Lane 1 of the Phase 4+5+8+15+16 parallel cycle. Phase 4 + Phase 5 must
land together because both modify the SetPolicy code path.

- daemon/src/lockout.rs — pure simulate(new_policy, registry) -> Vec<Violation>.
  Iterates Required stacks, flags users with no enrolled credential of any
  required method. 5 unit tests cover: optional-mode skipped, required-with-
  unenrolled flagged, any-method-satisfies, empty registry, multi-stack.
- daemon/src/policy_apply.rs — PolicyApplier renders the pam-configs profile
  (Default: yes when any stack requires fido2; pam_u2f.so + pam_authforge_pending
  when fido2 required, only pam_authforge_pending otherwise) and runs
  pam-auth-update --package. Stash-and-restore on failure: prior profile
  contents are restored and pam-auth-update re-run, so a failed apply leaves
  the system in its previous PAM state. 4 unit tests including a real-process
  rollback test against a failing /bin/sh shim.
- daemon/src/state.rs — AppState::set_policy(p, force) returns
  PolicyApplyResult. Always runs the simulator first; if violations and !force,
  returns { applied: false, violations } without writing. Otherwise persists
  via PolicyStore::save and invokes PolicyApplier::apply. StorageConfig grows
  pam_profile_path + pam_auth_update fields (env-var driven, tests inject a
  no-op /bin/sh shim into a tempdir).
- daemon/src/dbus.rs — SetPolicy signature is now (Policy, bool) -> Result.
  Wire-breaking pre-alpha; CLI updated in this commit.
- cli/src/{bus,commands}.rs — set_policy takes force flag. policy set runs
  with force=false and surfaces violations as a non-zero exit + stderr list
  pointing the user at policy apply --force-i-know-what-im-doing. policy
  apply now actually invokes pam-auth-update via the daemon.

Test count: 42 daemon (was 33; adds 5 lockout + 4 policy_apply). 13 common.
5 cli. cargo clippy --workspace --all-targets -D warnings clean.

Plan deviation: PolicyApplier::from_env() became PolicyApplier::new(profile_path,
pam_auth_update) with the env defaults moved into StorageConfig::from_env_or_defaults.
Cleaner: state owns one source of truth for env-driven path config.

daemon/src/main.rs

@@ -4,6 +4,8 @@ use tracing::{info, warn};
 
 mod dbus;
 mod fido;
+mod lockout;
+mod policy_apply;
 mod polkit;
 mod state;
 mod storage;