feat: add admin screens, permissions and navigation

Seven admin controllers in a "Studia BM" navigation group, guarded by
jz.bm.access_courses, jz.bm.access_schedule and jz.bm.access_materials,
with Polish and English labels. Date and time fields are checked by the
models before a save and answered as 422 on the field.

updates/updates_test.go

@@ -0,0 +1,43 @@
+package updates_test
+
+import (
+	"os"
+	"regexp"
+	"slices"
+	"strings"
+	"testing"
+
+	bm "git.golem15.com/jakub/sm-bm-plugin"
+)
+
+var migrationFile = regexp.MustCompile(`^(\d{14})_[a-z0-9_]+\.go$`)
+
+// The set must run in ID order (foreign keys point at earlier tables), and
+// every migration file is named after its ID.
+func TestMigrationOrder(t *testing.T) {
+	var ids []string
+	for _, m := range (&bm.Plugin{}).Migrations() {
+		if m.Migrate == nil || m.Rollback == nil {
+			t.Errorf("migration %s has no Migrate or Rollback", m.ID)
+		}
+		ids = append(ids, m.ID)
+	}
+	if !slices.IsSorted(ids) {
+		t.Errorf("migration IDs are not ascending: %v", ids)
+	}
+	entries, err := os.ReadDir(".")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var files []string
+	for _, e := range entries {
+		name := e.Name()
+		if e.IsDir() || !migrationFile.MatchString(name) {
+			continue
+		}
+		files = append(files, strings.TrimSuffix(name, ".go"))
+	}
+	if !slices.Equal(files, ids) {
+		t.Errorf("migration files %v, want one per ID %v", files, ids)
+	}
+}