max_response_body_size for http client

[stephenberry]

Add configurable body size limits for HTTP server and client

Closes #2417

Adds max_request_body_size (server) and max_response_body_size (client) to guard against memory exhaustion from oversized or malicious payloads. Both default to glz::http_default_max_body_size (100 MB).

Server

• New connection_config::max_request_body_size field with setter and getter on http_server.
• Requests whose Content-Length exceeds the limit are rejected with HTTP 413 before the body is allocated or read.
• Only applies to Content-Length-based requests (the server does not support chunked request Transfer-Encoding).

Client

• New http_client_error::response_too_large error code with a dedicated std::error_category.
• New http_client::max_response_body_size() setter and getter.
• Enforced in all four non-streaming response paths:
  • Sync Content-Length — checked before reading.
  • Sync chunked — checked before each chunk read.
  • Async Content-Length — checked before reading.
  • Async chunked — checked before each chunk read.
• Sockets are closed on rejection in all paths to prevent stale data in the connection pool.

Files changed

File	Change
include/glaze/net/http.hpp	http_default_max_body_size constant (100 MB)
include/glaze/net/http_server.hpp	max_request_body_size config, setter/getter, and 413 enforcement in finish_request()
include/glaze/net/http_client.hpp	http_client_error enum/category, max_response_body_size setter/getter, enforcement in sync and async paths
docs/networking/body-size-limits.md	Documentation page
mkdocs.yml	Wire new doc page into nav