feat(webui): bootstrap session handling and login process

pkg/model/session.go

@@ -0,0 +1,20 @@
+package model
+
+import (
+	"time"
+)
+
+type SessionContextKey struct{}
+
+type Session struct {
+	Id        string
+	AccountId int
+	Created   time.Time
+	Updated   time.Time
+	Data      any
+}
+
+func (session *Session) IsExpired() bool {
+	// TODO
+	return false
+}