fix: add pre-read guard to limitedReader to prevent state contamination

[Kunall7890]

What

Adds a strict pre-read guard to \limitedReader.Read\ that checks whether the read counter (
.read) already exceeds \LimitBytes\ before delegating to the underlying reader.

Why

The \limitedReader\ is reused via \sync.Pool\ in \BodyLimitWithConfig. While \Reset\ clears the counter, a contaminated \limitedReader\ retrieved from the pool could delegate reads to the underlying body without proper rejection if:

1. \Reset\ is not called before \Read\ (defensive against future refactoring)
2. A partial read sequence leaves
   .read\ at an intermediate value that still exceeds the limit

The post-read guard alone is insufficient because it only catches the overflow after it happens. The pre-read guard provides defense-in-depth: if
.read\ is already beyond the limit, fail immediately without touching the underlying stream.

Changes

\\diff
-func (r *limitedReader) Read(b []byte) (n int, err error) {

• n, err = r.reader.Read(b)
  +func (r *limitedReader) Read(p []byte) (n int, err error) {

• if r.read > r.LimitBytes {

•   return 0, echo.ErrStatusRequestEntityTooLarge
  

• }
• n, err = r.reader.Read(p)
  r.read += int64(n)
  if r.read > r.LimitBytes {
  return n, echo.ErrStatusRequestEntityTooLarge
  }
  return
  }
  \\

Closes #1