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/platform-bridge/webhook/adapter.go

@@ -1,7 +1,7 @@
 package webhook
 import (
 	"encoding/json"
-	"fmt"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/logger"
 	"net/http"
 	"time"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/platform-bridge"
@@ -31,5 +31,5 @@ func (a *Adapter) Stop() error { if a.server!=nil { a.server.Close() }; close(a.
 func (a *Adapter) Incoming() <-chan *bridge.UnifiedMessage { return a.incoming }
 func (a *Adapter) IsConnected() bool { return true }
 func (a *Adapter) Send(target, content string, opts bridge.SendOptions) error {
-	fmt.Printf("[webhook:%s] -> %s: %s\n", a.cfg.Name, target, content); return nil
+	logger.Infof("[webhook:%s] -> %s: %s\n", a.cfg.Name, target, content); return nil
 }