feat: add CreateExpenseListRequest DTO with validation to POST /create endpoint

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main/java/de/zendric/app/xpensely_server/controller/ExpenseListController.java

@@ -58,9 +58,11 @@ public class ExpenseListController {
     }
 
     @PostMapping("/create")
-    public ResponseEntity<ExpenseList> create(@RequestBody ExpenseList expenseList,
+    public ResponseEntity<ExpenseList> create(@RequestBody @Valid CreateExpenseListRequest request,
             Authentication authentication) {
         AppUser authenticatedUser = authenticatedUserResolver.resolveCurrentUser(authentication);
+        ExpenseList expenseList = new ExpenseList();
+        expenseList.setName(request.getName());
         expenseList.setOwner(authenticatedUser);
         XpenselyStandardCategories standardCategories = categoryService.getDefaultCategories();
         expenseList.setXpenselyStandardCategories(standardCategories);

src/main/java/de/zendric/app/xpensely_server/model/CreateExpenseListRequest.java

@@ -0,0 +1,17 @@
+package de.zendric.app.xpensely_server.model;
+
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Size;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@Getter
+@Setter
+@NoArgsConstructor
+public class CreateExpenseListRequest {
+
+    @NotBlank(message = "List name is required")
+    @Size(max = 100, message = "List name must not exceed 100 characters")
+    private String name;
+}