refactor: complete backend rewrite for multi-protocol proxy

Major rewrite of the Go backend to support:
- Three API format imports: openai, anthropic, compatible
- Three protocol conversions: Chat Completions, Responses, Messages
- Hub-and-spoke architecture with Chat as intermediate format

Deleted:
- opencat.go (old entry)
- store/, team/, pkg/team/, pkg/store/ (old data layer)
- internal/model/, internal/consts/ (old types)
- internal/service/team/, internal/controller/team/ (old handlers)
- llm/ (removed LLM client library, pure proxy mode)
- dist/, assets/ (old build artifacts)

Added:
- internal/store/ — 9 GORM models + multi-DB support
- internal/pkg/ — crypto (AES-GCM), apikey, jwt, ratelimit, resp, tokenizer
- internal/channel/ — channel selection, weighted LB, health checks
- internal/proxy/convert/ — 6 protocol conversion functions + SSE streaming
- internal/proxy/ — gateway with request dispatch and upstream selection
- internal/usage/ — async usage recorder with batch writes
- internal/api/ — management API (auth, users, keys, channels, models)
- Makefile for build/test/deploy

Fixed API to match frontend expectations:
- Login response wraps token in { data: { token } }
- GET /api/profile route added
- Profile response wraps user in { code, data }
- Role returned as number (10=admin, 1=user)

cmd/openteam/main.go

@@ -6,16 +6,13 @@ import (
 	"io/fs"
 	"log"
 	"opencatd-open/internal/cli"
-	"opencatd-open/internal/consts"
+	"opencatd-open/internal/store"
 	"opencatd-open/pkg/config"
-	"opencatd-open/pkg/store"
 	"opencatd-open/router"
 
 	"github.com/spf13/cobra"
 )
 
-// all:dist 使 dist 只含 .gitkeep 占位（尚未构建前端）时也能编译通过，
-// 本地 go run ./cmd/openteam 无需先跑 pnpm build
 //go:embed all:dist
 var web embed.FS
 
@@ -29,11 +26,11 @@ func main() {
 	if err != nil {
 		panic(err)
 	}
+	_ = db
 
 	rootCmd := &cobra.Command{
 		Use:   "openteam",
 		Short: "openteam cli",
-		Long:  consts.Logo,
 		Run: func(cmd *cobra.Command, args []string) {
 			router.SetRouter(cfg, db, &web)
 		},
@@ -50,7 +47,6 @@ func printFilesAndDirs(fsys fs.FS, prefix string) error {
 		if err != nil {
 			return err
 		}
-
 		if d.IsDir() {
 			fmt.Printf("%s[DIR] %s\n", prefix, p)
 		} else {