support nginx-1.31.0

[yuwenlong]

Summary

Add proxy_connect_rewrite_103100.patch for nginx 1.31.0 compatibility.

Key Changes

• ngx_http_parse.c: No changes needed — nginx 1.31.0 already has native CONNECT parsing that routes to sw_spaces_before_host and handles host:port via the standard state machine.
• ngx_http_request.c: Reuses nginx 1.31.0's built-in host/port processing (r->headers_in.server and r->port) to populate r->connect_host and r->connect_port_n, instead of duplicating parse logic.
• ngx_http_request.c: Wraps nginx 1.31.0's conditional CONNECT rejection (allow_connect check) with #if !(NGX_HTTP_PROXY_CONNECT).
• ngx_http_request.h: Adds connect_host, connect_port, connect_port_n fields. Raw parse pointers not needed since nginx 1.31.0's native parser handles CONNECT.
• ngx_http_variables.c: Adds connect_host and connect_port variables.
• Uses the new 4-argument ngx_http_validate_host API from nginx 1.31.0.

All hunks apply cleanly to nginx 1.31.0.