refactor(ecstore): migrate config globals into ECStore struct fields (#3219)

* refactor(ecstore): migrate config globals into ECStore struct fields

Phase 2 of global singleton consolidation. Add server_config and
storage_class fields to ECStore, sharing the same underlying data
as the process-global LazyLock statics.

New ECStore fields:
- server_config: RwLock<Option<Config>>
- storage_class: RwLock<storageclass::Config>

New async accessor methods:
- get_server_config() / set_server_config()
- get_storage_class() / set_storage_class()

Fields initialized with defaults in ECStore::new(), synced from
globals after init() completes. Global functions preserved for
backward compatibility.

1160 tests pass, clippy clean, full workspace compiles.

* fix: address PR #3219 review comments - delegate to globals

Accessors now delegate to process-global statics to avoid state drift:
- get_server_config() delegates to get_global_server_config()
- set_server_config() updates both global and local field
- get_storage_class() delegates to get_global_storage_class()
- set_storage_class() updates both global and local field
- Removed stale sync code from init()
- Changed fields to std::sync::RwLock for sync access

1160 tests pass.

* fix: correct import order for cargo fmt

* fix: simplify config accessors - delegate to globals without local state

Remove local server_config and storage_class fields from ECStore.
Accessors now purely delegate to process-global statics, eliminating
the state drift risk identified in review.

1160 tests pass, formatting clean.

crates/ecstore/src/store.rs

@@ -206,6 +206,31 @@ impl std::fmt::Debug for ECStore {
     }
 }
 
+/// Phase 2: Accessor methods for config globals
+/// These delegate to the process-global statics. No local state — the globals
+/// remain the single source of truth until the migration is complete.
+impl ECStore {
+    /// Get server configuration (delegates to global)
+    pub fn get_server_config(&self) -> Option<crate::config::Config> {
+        crate::config::get_global_server_config()
+    }
+
+    /// Set server configuration (delegates to global)
+    pub fn set_server_config(&self, cfg: crate::config::Config) {
+        crate::config::set_global_server_config(cfg);
+    }
+
+    /// Get storage class configuration (delegates to global)
+    pub fn get_storage_class(&self) -> Option<crate::config::storageclass::Config> {
+        crate::config::get_global_storage_class()
+    }
+
+    /// Set storage class configuration (delegates to global)
+    pub fn set_storage_class(&self, cfg: crate::config::storageclass::Config) {
+        crate::config::set_global_storage_class(cfg);
+    }
+}
+
 // impl Clone for ECStore {
 //     fn clone(&self) -> Self {
 //         let pool_meta = match self.pool_meta.read() {