refactor(admin): move site-replication service core out of handlers (#6699)

Mechanical move-only extraction for backlog#1840 PR1+PR4: the site-replication state (load/parse/persist/RMW transaction), repair state machine, peer transport (client cache, DNS resolver, send_peer_* family), retry queue, and the four storage-side hooks move from rustfs/src/admin/handlers/site_replication.rs into the new infra-layer module rustfs/src/site_replication/ ({mod,state,state_lock,identity,transport,retry,repair,hooks}.rs). The admin handler file keeps route registration, all Operation impls, request/response glue, and the in-file test module, and re-exports the moved items so existing paths keep resolving. admin/site_replication_identity.rs and admin/site_replication_state.rs relocate wholesale as identity.rs/state_lock.rs.

Storage access from the moved code goes through a new site_replication consumer module in the root facade (rustfs/src/storage_api.rs), including an s3 shim so the module stays off the direct s3s surface (file count stays at the 215 baseline). The three admin runtime-source wrappers the moved code needs (outbound TLS generation incl. the test atomic, outbound TLS state, runtime port) are reproduced locally; the TLS-generation trio moves out of admin/runtime_sources.rs since site replication was its only consumer. The one non-verbatim rewrite: site_replication_peer_payload inlines encrypt_stream_io in its encrypted branch, which is provably the branch encode_compatible_admin_payload always took for the /minio/admin peer-join wire path.

app/bucket_usecase.rs now imports the three bucket hooks from crate::site_replication, deleting the three app->interface entries from the layer baseline (shrink-only). The peer-client cache test moves with the owner-local SITE_REPLICATION_PEER_CLIENT static into transport.rs (228+1 = 229 tests conserved). New module files are added to the logging-guardrail checked list; the s3_error! line baseline tightens 1620 -> 1619; global-state/config-consumer inventories and ARCHITECTURE.md pointers updated.

Verified: cargo check -p rustfs --all-targets clean; cargo clippy --workspace --all-targets clean; cargo nextest run -p rustfs --lib 3852/3852 passed; make pre-commit green; scripts/check_layer_dependencies.sh green with baseline-only deletions; line-multiset conservation audit over the moved code accounts for every non-verbatim line (visibility bumps, import rewrites, fmt reflow).

Refs rustfs/backlog#1840

docs/architecture/ecstore-config-consumer-inventory.md

@@ -123,7 +123,7 @@ behind narrower contracts.
 | Files | Current usage |
 |---|---|
 | `rustfs/src/admin/handlers/kms_dynamic.rs` | Uses generic `read_config` and `save_config` for dynamic KMS config objects. |
-| `rustfs/src/admin/handlers/site_replication.rs` | Uses generic `read_config`, `save_config`, and `delete_config` for site-replication state objects. |
+| `rustfs/src/site_replication/state.rs` | Uses generic `read_config`, `save_config`, and `delete_config` (via the root storage facade) for site-replication state objects. |
 | `rustfs/src/admin/service/site_replication.rs` | Uses generic `read_config` and `save_config` for site-replication state normalization. |
 | `rustfs/src/server/module_switch.rs` | Uses generic `read_config` and `save_config` for module-switch config objects. |
 | `crates/iam/src/store/object.rs` | Uses generic `read_config_no_lock`, `read_config_with_metadata`, `save_config`, `save_config_with_opts`, and `delete_config` helper variants for IAM object-store persistence paths. |

docs/architecture/global-state-inventory.md

@@ -110,11 +110,11 @@ inventory. Generic function-local names such as `CACHE`, `LOCK`, `INIT`, and
 | `GET_OBJECT_BUFFER_THRESHOLD_WARNED`, `GET_READER_STREAM_BUFFER_SIZE_OVERRIDE`, function-local `ENABLED`, `OBJECT_SEEK_SUPPORT_THRESHOLD`, `OBJECT_SEEK_SUPPORT_CONCURRENCY_THRESHOLDS` | `rustfs/src/app/object/get.rs` | Cache or constant / owner-local cache | Object GET/seek tuning caches and warning guards stay private to object usecase helpers. |
 | `SUPPORTED_HEADERS` | `rustfs/src/storage/options.rs` | Cache or constant / owner-local constant | Supported-header lookup state stays private to storage option parsing. |
 | `AUDIT_TARGET_SPECS`, `NOTIFICATION_TARGET_SPECS` | `rustfs/src/admin/handlers/audit.rs`, `rustfs/src/admin/handlers/event.rs`, `rustfs/src/admin/handlers/plugins_instances.rs` | Cache or constant / owner-local constant | Admin target descriptor tables stay private to their handler owners. |
-| `SITE_REPLICATION_PEER_CLIENT` | `rustfs/src/admin/handlers/site_replication.rs` | Process-global owner-local cache | Site-replication peer client cache stays private to site-replication handlers. The state RMW transaction holds no process-local mutex — see `rustfs/src/admin/site_replication_state.rs`. |
+| `SITE_REPLICATION_PEER_CLIENT` | `rustfs/src/site_replication/transport.rs` | Process-global owner-local cache | Site-replication peer client cache stays private to the site-replication transport module. The state RMW transaction holds no process-local mutex — see `rustfs/src/site_replication/state_lock.rs`. |
 | `AUDIT_MODULE_ENABLED`, `NOTIFY_MODULE_ENABLED`, `PERSISTED_NOTIFY_MODULE_ENABLED`, `PERSISTED_AUDIT_MODULE_ENABLED`, `PERSISTED_MODULE_SWITCH_CONFIGURED` | `rustfs/src/server/audit.rs`, `rustfs/src/server/event.rs`, `rustfs/src/server/module_switch.rs` | Process-global owner-local toggles | Audit/notify module snapshots stay private to the server module switch owners. |
 | `DELETE_TAIL_TOTAL`, `DELETE_CLEANUP_TOTAL`, `DELETE_REPLICATION_TOTAL`, `DELETE_NOTIFY_TOTAL` | `rustfs/src/delete_tail_activity.rs` | Process-global owner-local counters | Delete-tail activity counters stay private behind delete-tail activity helpers. |
 | `EMBEDDED_SERVER_STARTED` | `rustfs/src/startup_lifecycle.rs` | Process-global owner-local guard | Embedded startup single-start protection stays private to startup lifecycle. |
-| `TEST_OUTBOUND_TLS_GENERATION` | `rustfs/src/admin/runtime_sources.rs` | Test or fixture state | Outbound TLS generation test hook state stays private to admin runtime-source tests. |
+| `TEST_OUTBOUND_TLS_GENERATION` | `rustfs/src/site_replication/mod.rs` | Test or fixture state | Outbound TLS generation test hook state stays private to site-replication transport tests. |
 | `TEST_REMAINING_FAILURES` | `rustfs/src/startup_iam.rs` | Test or fixture state | IAM startup retry injection state stays private to debug/test startup code. |
 | `CAPACITY_DIRTY_SCOPE_ENV`, `CAPACITY_DIRTY_SCOPE_INIT`, `GLOBAL_ENV`, function-local `INIT` | `rustfs/src/app/*_test.rs` | Test or fixture state | App integration test fixture state stays private to the owning test modules. |