feat: 平台配置唯一ID — PlatformConfig.ID + adapter全链路传播

- PlatformConfig 新增 ID 字段 (8字节hex，创建时自动生成)
- QQ adapter 新增 configID + ConfigID() 访问器
- ChannelInfo 新增 AdapterID + AdapterName
- createSingleAdapter 接受 configID 参数
- 同一个平台类型的多个配置实例通过 ID 唯一区分

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

backend/platform-bridge/internal/config/store.go

@@ -1,6 +1,8 @@
 package config
 
 import (
+	"crypto/rand"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"os"
@@ -10,11 +12,13 @@ import (
 
 // PlatformConfig holds persistent configuration for one platform adapter.
 type PlatformConfig struct {
-	Name      string            `json:"name"`
-	Platform  string            `json:"platform"` // base platform type: "qq", "telegram", etc.
+	ID        string            `json:"id"`        // immutable unique ID, generated at creation
+	Name      string            `json:"name"`      // config key, e.g. "qq-main", "qq-work"
+	Platform  string            `json:"platform"`  // base platform type: "qq", "telegram", etc.
 	Enabled   bool              `json:"enabled"`
 	Label     string            `json:"label"`
 	Fields    map[string]string `json:"fields"`
+	CreatedAt time.Time         `json:"created_at"`
 	UpdatedAt time.Time         `json:"updated_at"`
 }
 
@@ -102,11 +106,22 @@ func (s *Store) Set(cfg PlatformConfig) error {
 	if cfg.Fields == nil {
 		cfg.Fields = make(map[string]string)
 	}
+	// Generate stable ID for new configs.
+	if cfg.ID == "" {
+		cfg.ID = generateConfigID()
+		cfg.CreatedAt = time.Now()
+	}
 	cfg.UpdatedAt = time.Now()
 	s.configs[cfg.Name] = &cfg
 	return s.save()
 }
 
+func generateConfigID() string {
+	b := make([]byte, 8)
+	rand.Read(b)
+	return hex.EncodeToString(b)
+}
+
 // Delete removes a platform config and persists.
 func (s *Store) Delete(name string) error {
 	s.mu.Lock()