style: Apply cargo fix for unused variables

server/src/handlers/graph.rs

@@ -165,7 +165,7 @@ impl McpTool for CreateEntitiesHandler {
         state.modify_graph(|g| {
             for entity_input in req.entities {
                 if !entity_input.name.is_empty() {
-                    let mut entity = crate::models::Entity {
+                    let entity = crate::models::Entity {
                         name: entity_input.name.clone(),
                         entity_type: crate::models::normalize_entity_type(&entity_input.entity_type),
                         observations: entity_input.observations,
@@ -264,7 +264,7 @@ impl McpTool for CreateRelationsHandler {
             }
             for relation_input in req.relations {
                 if !relation_input.from.is_empty() && !relation_input.to.is_empty() {
-                    let mut relation = crate::models::Relation {
+                    let relation = crate::models::Relation {
                         from: relation_input.from,
                         to: relation_input.to,
                         relation_type: crate::models::normalize_relation_type(&relation_input.relation_type),