feat(config): add system configuration module (Phase 3)

Implement the complete erp-config crate with:
- Data dictionaries (CRUD + items management)
- Dynamic menus (tree structure with role filtering)
- System settings (hierarchical: platform > tenant > org > user)
- Numbering rules (concurrency-safe via PostgreSQL advisory_lock)
- Theme and language configuration (via settings store)
- 6 database migrations (dictionaries, menus, settings, numbering_rules)
- Frontend Settings page with 5 tabs (dictionary, menu, numbering, settings, theme)

Refactor: move RBAC functions (require_permission) from erp-auth to erp-core
to avoid cross-module dependencies.

Add 20 new seed permissions for config module operations.

crates/erp-server/migration/src/lib.rs

@@ -11,6 +11,12 @@ mod m20260411_000008_create_user_roles;
 mod m20260411_000009_create_organizations;
 mod m20260411_000010_create_departments;
 mod m20260411_000011_create_positions;
+mod m20260412_000012_create_dictionaries;
+mod m20260412_000013_create_dictionary_items;
+mod m20260412_000014_create_menus;
+mod m20260412_000015_create_menu_roles;
+mod m20260412_000016_create_settings;
+mod m20260412_000017_create_numbering_rules;
 
 pub struct Migrator;
 
@@ -29,6 +35,12 @@ impl MigratorTrait for Migrator {
             Box::new(m20260411_000009_create_organizations::Migration),
             Box::new(m20260411_000010_create_departments::Migration),
             Box::new(m20260411_000011_create_positions::Migration),
+            Box::new(m20260412_000012_create_dictionaries::Migration),
+            Box::new(m20260412_000013_create_dictionary_items::Migration),
+            Box::new(m20260412_000014_create_menus::Migration),
+            Box::new(m20260412_000015_create_menu_roles::Migration),
+            Box::new(m20260412_000016_create_settings::Migration),
+            Box::new(m20260412_000017_create_numbering_rules::Migration),
         ]
     }
 }