Integrate and configure BearerAuthConfig for MCP

## Description:
Configure Volga bearer authentication to match MCP expectations.

## Scope:

- `require_audience(canonical_uri)`
- `require_https(true)`
- `with_resource_metadata_url(...)`
- Rely on Volga default `strip_token_from_request = true`
- Remove manual `Authorization` header stripping

## Goal:
Ensure secure and spec-aligned token validation with minimal user configuration.