🐛 [Bug]: `app.Use` breaks when using `NewWithCustomCtx`

[febelery]

Bug Description

Bug: app.Use breaks when using NewWithCustomCtx

Description

When using fiber.NewWithCustomCtx, any app.Use() middleware causes a panic or context type assertion failure.
Without app.Use, the app works correctly and custom context methods can be used normally.

Example Code

package main

import (
	"log"

	"github.com/gofiber/fiber/v3"
)

type CustomCtx struct {
	fiber.DefaultCtx
}

func (c *CustomCtx) CustomMethod() string {
	return "custom value"
}

func main() {
	app := fiber.NewWithCustomCtx(func(app *fiber.App) fiber.CustomCtx {
		return &CustomCtx{
			DefaultCtx: *fiber.NewDefaultCtx(app),
		}
	})

	app.Use(func(c fiber.Ctx) error {
		return c.Next()
	})

	app.Get("/:id", func(c fiber.Ctx) error {
		customCtx, ok := c.(*CustomCtx)
		if !ok {
			return c.SendString("error")
		}
		return c.SendString(customCtx.CustomMethod())
	})

	log.Fatal(app.Listen(":8080"))
}

How to Reproduce

app.Use(func(c fiber.Ctx) error {
return c.Next()
})

Expected Behavior

package main

import (
	"log"

	"github.com/gofiber/fiber/v3"
)

type CustomCtx struct {
	fiber.DefaultCtx
}

func (c *CustomCtx) CustomMethod() string {
	return "custom value"
}

func main() {
	app := fiber.NewWithCustomCtx(func(app *fiber.App) fiber.CustomCtx {
		return &CustomCtx{
			DefaultCtx: *fiber.NewDefaultCtx(app),
		}
	})

	app.Get("/:id", func(c fiber.Ctx) error {
		customCtx, ok := c.(*CustomCtx)
		if !ok {
			return c.SendString("error")
		}

		return c.SendString(customCtx.CustomMethod())
	})

	log.Fatal(app.Listen(":8080"))
}

Fiber Version

v3.0.0-rc2

Code Snippet (optional)

package main

import (
	"log"

	"github.com/gofiber/fiber/v3"
)

type CustomCtx struct {
	fiber.DefaultCtx
}

func (c *CustomCtx) CustomMethod() string {
	return "custom value"
}

func main() {
	app := fiber.NewWithCustomCtx(func(app *fiber.App) fiber.CustomCtx {
		return &CustomCtx{
			DefaultCtx: *fiber.NewDefaultCtx(app),
		}
	})

	app.Use(func(c fiber.Ctx) error {
		return c.Next()
	})

	app.Get("/:id", func(c fiber.Ctx) error {
		customCtx, ok := c.(*CustomCtx)
		if !ok {
			return c.SendString("error")
		}

		return c.SendString(customCtx.CustomMethod())
	})

	log.Fatal(app.Listen(":8080"))
}

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my problem prior to opening this one.
• I understand that improperly formatted bug reports may be closed without explanation.