refactor: rebrand from cs-agent to BossChat

- Rename Go module: cs-agent → bosschat
- Rename all import paths across 200+ Go files
- Rename SDK: cs-ai-agent-sdk → bosschat-sdk
- Rename message protocol: cs-agent:* → bosschat:*
- Rename JS globals: CSAgentConfig → BossChatConfig
- Rename CSS classes: cs-agent-* → bosschat-*
- Update Makefile APP_NAME and ARCHIVE_NAME
- Update logo assets
- Fix display name: BoosChat → BossChat

cmd/testdata/aiagent/init.go

@@ -1,11 +1,11 @@
 package aiagent
 
 import (
-	"cs-agent/cmd/testdata/skill"
-	"cs-agent/internal/models"
-	"cs-agent/internal/pkg/enums"
-	"cs-agent/internal/pkg/utils"
-	"cs-agent/internal/repositories"
+	"bosschat/cmd/testdata/skill"
+	"bosschat/internal/models"
+	"bosschat/internal/pkg/enums"
+	"bosschat/internal/pkg/utils"
+	"bosschat/internal/repositories"
 	"fmt"
 	"time"