created tracker api endpoint and created UI interface for trackers

server/internal/models/tracker.go

@@ -0,0 +1,11 @@
+package models
+
+import "time"
+
+type Tracker struct {
+	GUID      string `gorm:"primaryKey"`
+	Name      string `gorm:"size:255;not null"`
+	Users     []User `gorm:"many2many:user_trackers;constraint:OnDelete:CASCADE;"`
+	CreatedAt time.Time
+	UpdatedAt time.Time
+}