refactor: Gitea 式目录改组，移除本分支 SPA 与杂项产物

将 model/service/handler/middleware 迁至 models/services/routers/api/modules/auth，并删除 frontend、embed_static、scripts 及误入库缓存/二进制。

Co-authored-by: Cursor <cursoragent@cursor.com>

services/mention_test.go

@@ -0,0 +1,14 @@
+package service
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestExtractMentionNames(t *testing.T) {
+	got := ExtractMentionNames("hi @alice 和 @小明_x 以及 @bob-1")
+	want := []string{"alice", "小明_x", "bob-1"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("got %#v, want %#v", got, want)
+	}
+}