fix(middleware): halt execution chain immediately after writing error response (#1)

[AKASH80047]

Description

Fixes #1

Summary of Changes:

• Explicit Early Return: Added explicit
  eturn\ statements immediately following \http.Error\ and header response writes across all middleware implementations (\AuthMiddleware, \RequireHeader, \BasicAuth).
• Superfluous Header Elimination: Completely prevents \superfluous response.WriteHeader\ warnings and eliminates unintended fallthrough to downstream handlers.
• Comprehensive Unit Testing (\middleware/auth_test.go): Verifies that rejected requests immediately halt the chain and bypass downstream spy handlers.

/claim #1