Replace os.exit with wails quit

Exit would prevent defers from running which meant db would be left
dangling

app.go

@@ -2,7 +2,8 @@ package main
 
 import (
 	"context"
-	"os"
+
+	"github.com/wailsapp/wails/v2/pkg/runtime"
 )
 
 // App struct
@@ -139,5 +140,5 @@ func (a *App) SetSetting(key string, value int64) WailsGenericAck {
 
 //region other
 func (a *App) Close() {
-	os.Exit(0)
+	runtime.Quit(a.ctx)
 }