feat: 同平台多账号支持 — adapter_name 贯穿全链路

- UnifiedMessage 新增 AdapterName 字段
- router 从适配器 ConfigName() 捕获 adapter 实例名
- forwardToAICore source 新增 adapter_name
- ai-core SetBotUID key 优先用 adapter_name，回退 platform
- 更新优化大纲加入 P4.1

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

backend/platform-bridge/internal/bridge/router.go

@@ -150,6 +150,11 @@ func (r *PlatformRouter) RouteMessage(adapterKey string, rawMsg interface{}) (*U
 		unified.BotUID = selfAware.SelfID()
 	}
 
+	// Capture adapter config name for multi-account routing.
+	if named, ok := a.(interface{ ConfigName() string }); ok {
+		unified.AdapterName = named.ConfigName()
+	}
+
 	// Resolve identity (nil for unknown users; caller decides routing).
 	// Use platform type (e.g. "qq") for identity resolution, not adapter key.
 	identity := r.mapper.ResolveOrNil(a.PlatformName(), unified.SenderID)