fix(group): register auto 404 routes only once on Use

[Solaris-star]

Description

After #2996, Group.Use auto-registers RouteNotFound catch-alls so group middleware still runs on 404s. It did that on every Use() call.

With AllowOverwritingRoute: false (or whenever duplicate routes are rejected), a second Use panics:

panic: echo_route_not_found /api: adding duplicate route (same method+path) is not allowed

Repro patterns from #3047:

g := e.Group("/api")
g.Use(mw1)
g.Use(mw2) // panic

g := e.Group("/api", mw1)
g.Use(mw2) // panic

Fix

Only auto-register the 404 routes the first time the group gains middleware (hadMiddleware was empty before append). Subsequent Use calls only append middleware.

Tests

go test ./... -count=1

Added TestGroup_UseMultipleTimesDoesNotPanic.

Linked Issue

Closes #3047

[aldas]

Thanks, closing, #3049 implemented a little bit different approach