refactor(logging): replace all print/log with structured slog logger

- main.go: 30+ log.Printf → logger.Infof
- plugin/registry: 12 log.Printf → logger.Infof
- db/db.go, ws/hub.go: log → logger
- platform-bridge: fmt.Printf/println → logger.Info
- Logs now: time=... level=INFO msg=...
- 16 packages pass, vet clean

backend/services/gateway/ws/hub.go

@@ -4,7 +4,7 @@ package ws
 import (
 	"context"
 	"encoding/json"
-	"log"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/logger"
 	"net/http"
 	"sync"
 
@@ -76,7 +76,7 @@ func (h *Hub) run() {
 			h.clients[c] = true
 			n := len(h.clients)
 			h.mu.Unlock()
-			log.Printf("[ws] client connected (total=%d)", n)
+			logger.Infof("[ws] client connected (total=%d)", n)
 
 		case c := <-h.unregister:
 			h.mu.Lock()
@@ -103,7 +103,7 @@ func (h *Hub) run() {
 func (h *Hub) HandleUpgrade(w http.ResponseWriter, r *http.Request) {
 	conn, err := upgrader.Upgrade(w, r, nil)
 	if err != nil {
-		log.Printf("[ws] upgrade error: %v", err)
+		logger.Infof("[ws] upgrade error: %v", err)
 		return
 	}