step 1: rename module chat-switchboard → switchboard-core

- go.mod module name
- All 714 import references across 289 Go files
- VERSION: 0.1.0
- CI DB names: switchboard_core_{ci,dev,test}
- Docker image: gobha/switchboard-core
- Test fixtures: JWT issuer, repo names
- .env.example, docker-compose container name
- Compiles clean (go build exit 0)

server/store/postgres/message_tree.go

@@ -6,8 +6,8 @@ import (
 	"encoding/json"
 	"fmt"
 
-	"chat-switchboard/models"
-	"chat-switchboard/store"
+	"switchboard-core/models"
+	"switchboard-core/store"
 )
 
 // ── Tree Operations (v0.29.0) ───────────────────────────────────────────