feat(core): implement optimistic locking across all entities

Add VersionMismatch error variant and check_version() helper to erp-core.
All 13 mutable entities now enforce version checking on update/delete:
- erp-auth: user, role, organization, department, position
- erp-config: dictionary, dictionary_item, menu, setting, numbering_rule
- erp-workflow: process_definition, process_instance, task
- erp-message: message, message_subscription

Update DTOs to expose version in responses and require version in update
requests. HTTP 409 Conflict returned on version mismatch.

crates/erp-auth/src/dto.rs

@@ -38,6 +38,7 @@ pub struct UserResp {
     pub avatar_url: Option<String>,
     pub status: String,
     pub roles: Vec<RoleResp>,
+    pub version: i32,
 }
 
 #[derive(Debug, Deserialize, Validate, ToSchema)]
@@ -58,6 +59,7 @@ pub struct UpdateUserReq {
     pub phone: Option<String>,
     pub display_name: Option<String>,
     pub status: Option<String>,
+    pub version: i32,
 }
 
 // --- Role DTOs ---
@@ -69,6 +71,7 @@ pub struct RoleResp {
     pub code: String,
     pub description: Option<String>,
     pub is_system: bool,
+    pub version: i32,
 }
 
 #[derive(Debug, Deserialize, Validate, ToSchema)]
@@ -84,6 +87,7 @@ pub struct CreateRoleReq {
 pub struct UpdateRoleReq {
     pub name: Option<String>,
     pub description: Option<String>,
+    pub version: i32,
 }
 
 #[derive(Debug, Deserialize, ToSchema)]
@@ -120,6 +124,7 @@ pub struct OrganizationResp {
     pub level: i32,
     pub sort_order: i32,
     pub children: Vec<OrganizationResp>,
+    pub version: i32,
 }
 
 #[derive(Debug, Deserialize, Validate, ToSchema)]
@@ -136,6 +141,7 @@ pub struct UpdateOrganizationReq {
     pub name: Option<String>,
     pub code: Option<String>,
     pub sort_order: Option<i32>,
+    pub version: i32,
 }
 
 // --- Department DTOs ---
@@ -151,6 +157,7 @@ pub struct DepartmentResp {
     pub path: Option<String>,
     pub sort_order: i32,
     pub children: Vec<DepartmentResp>,
+    pub version: i32,
 }
 
 #[derive(Debug, Deserialize, Validate, ToSchema)]
@@ -169,6 +176,7 @@ pub struct UpdateDepartmentReq {
     pub code: Option<String>,
     pub manager_id: Option<Uuid>,
     pub sort_order: Option<i32>,
+    pub version: i32,
 }
 
 // --- Position DTOs ---
@@ -181,6 +189,7 @@ pub struct PositionResp {
     pub code: Option<String>,
     pub level: i32,
     pub sort_order: i32,
+    pub version: i32,
 }
 
 #[derive(Debug, Deserialize, Validate, ToSchema)]
@@ -198,4 +207,5 @@ pub struct UpdatePositionReq {
     pub code: Option<String>,
     pub level: Option<i32>,
     pub sort_order: Option<i32>,
+    pub version: i32,
 }