refactor(ecstore): move object_lock WORM evaluation onto storage-level types (#6666)

The object_lock module evaluated WORM state through s3s wire DTOs (ObjectLockRetention, ObjectLockLegalHold, DefaultRetention, Date) and s3s header constants, keeping the storage engine coupled to the serving protocol (rustfs/backlog#1842, ARCHITECTURE.md invariant 4). This PR gives the module its own storage-level vocabulary and pushes the DTO conversions to the boundaries that already speak s3s.

New crates/ecstore/src/bucket/object_lock/types.rs defines RetentionMode, LegalHoldStatus, ObjectRetention, ObjectLegalHold, and DefaultRetention with no s3s dependency. objectlock.rs parses persisted metadata into these types using the rustfs-utils lowercase header constants (the same literal keys as before, pinned by the existing g-key-002 test). objectlock_sys.rs evaluates retention/legal-hold/default-retention from them; the fail-closed error messages and decision logic are unchanged line for line where possible.

Boundary conversions:
- bucket/metadata_sys.rs gains default_retention_from_object_lock_config, converting the persisted s3s configuration into the storage-level DefaultRetention; a rule without a usable GOVERNANCE/COMPLIANCE mode converts to None exactly like the evaluation code always ignored it, and days/years pass through so an invalid period still fails closed at evaluation time.
- check_object_lock_for_deletion_with_config becomes check_object_lock_for_deletion_with_default_retention (it only ever read the default retention); the lifecycle object_lock_boundary keeps the old s3s-typed signature and converts.
- The ObjectLockApi / ObjectLockStatusExt trait impls for the s3s DTOs move next to the persisted configuration owner in bucket/metadata.rs; the traits stay in object_lock/mod.rs.
- check_retention_for_modification now takes Option<RetentionMode>. The serving-layer wrappers (rustfs storage_api, set_disk options path) convert the request string with the new RetentionMode::parse_exact, which accepts only the canonical spelling — preserving the historical literal comparison where a non-canonical requested mode reads as a mode change and stays blocked.
- rustfs app-layer wrappers return the storage types; the replication-overwrite gate in object_usecase.rs uses the typed API (legal_hold.is_on(), RetentionMode::Compliance).

Ratchet: the ecstore-scoped s3s counter drops 42 -> 39 and the repo-wide file counter 211 -> 208 in scripts/check_s3s_footprint.sh.

Verification: cargo check -p rustfs-ecstore --all-targets and -p rustfs (lib+bins); cargo clippy -p rustfs-ecstore --all-targets and -p rustfs --lib --bins (clean); cargo nextest run -p rustfs-ecstore --no-fail-fast (4534/4542; the 8 failures are the same store::rebalance / store::heal machine-baseline set that fails identically on pristine origin/main, plus one fencing flake that passes in isolation); all object_lock/retention/legal-hold tests pass; guard scripts (layer deps, migration rules, s3s footprint, logging, error-format ratchet, doc paths) pass.

crates/ecstore/src/set_disk/mod.rs

@@ -46,8 +46,8 @@ use crate::bucket::lifecycle::lifecycle::TRANSITION_COMPLETE;
 use crate::bucket::metadata_sys;
 use crate::bucket::metadata_sys::ObjectLockConfigState;
 use crate::bucket::object_lock::objectlock_sys::{
-    check_object_lock_for_deletion_with_config, check_object_lock_for_deletion_with_state, check_retention_for_modification,
-    replication_write_may_pass_worm_gate,
+    check_object_lock_for_deletion_with_default_retention, check_object_lock_for_deletion_with_state,
+    check_retention_for_modification, replication_write_may_pass_worm_gate,
 };
 use crate::bucket::replication::{
     ReplicateDecision, ReplicationObjectBridge, ReplicationState, ReplicationStatusType, VersionPurgeStatusType,
@@ -4688,7 +4688,10 @@ fn check_object_lock_retention_update(bucket: &str, object: &str, obj_info: &Obj
     if let Some(retention) = &opts.object_lock_retention
         && check_retention_for_modification(
             &obj_info.user_defined,
-            retention.mode.as_deref(),
+            retention
+                .mode
+                .as_deref()
+                .and_then(crate::bucket::object_lock::types::RetentionMode::parse_exact),
             retention.retain_until,
             retention.bypass_governance,
         )