feat(api): lowercase project identifier before by-index lookup

Normalises the input side so GitHub-style references like "TEST1-42" and
"test1-42" resolve to the same project. The SQL comparison itself remains
case-sensitive for now; case-insensitive matching on the column will be
addressed separately.

pkg/routes/resolve_project.go

@@ -19,6 +19,7 @@ package routes
 import (
 	"net/http"
 	"strconv"
+	"strings"
 
 	"code.vikunja.io/api/pkg/db"
 	"code.vikunja.io/api/pkg/models"
@@ -44,7 +45,7 @@ func ResolveProjectIdentifier() echo.MiddlewareFunc {
 
 			s := db.NewSession()
 			project := &models.Project{}
-			has, err := s.Where("identifier = ?", raw).Get(project)
+			has, err := s.Where("identifier = ?", strings.ToLower(raw)).Get(project)
 			_ = s.Close()
 			if err != nil {
 				return err

pkg/webtests/task_by_index_test.go

@@ -57,6 +57,12 @@ func TestTaskByProjectIndex(t *testing.T) {
 		assert.Contains(t, rec.Body.String(), `"id":1`)
 	})
 
+	t.Run("identifier match is case-insensitive on the input", func(t *testing.T) {
+		rec := do("/api/v1/projects/TEST1/tasks/by-index/1")
+		assert.Equal(t, http.StatusOK, rec.Code)
+		assert.Contains(t, rec.Body.String(), `"id":1`)
+	})
+
 	t.Run("unknown project identifier returns 404", func(t *testing.T) {
 		rec := do("/api/v1/projects/does-not-exist/tasks/by-index/1")
 		assert.Equal(t, http.StatusNotFound, rec.Code)