Address code review feedback for HTTP client and server

Based on code review feedback:

Client improvements:
- Remove redundant capacity check in http_client_get_builder
  (already verified num_conns < capacity)
- Fix generation counter - no longer reset to zero when allocating
  connections, only incremented on request send
- Add HTTP_Method parameter to http_request_builder_url instead
  of hardcoding GET method
- Free connection resources when http_request_builder_send fails
  (invalid host mode or socket_connect failure)

Server bug fix:
- Fix ready queue indexing in http_server_next_request
  Changed: &server->conns[server->ready_head]
  To: &server->conns[server->ready[server->ready_head]]
  This bug would have caused incorrect connection retrieval

All changes maintain consistency with the codebase style and
improve robustness of error handling.

Makefile

@@ -6,7 +6,7 @@ chttp.c chttp.h: $(wildcard src/*.c src/*.h) misc/amalg.py Makefile
 	python misc/amalg.py
 
 example: main.c chttp.c chttp.h
-	gcc main.c chttp.c -o example -Wfatal-errors -DHTTPS_ENABLED -lcrypto -lssl
+	gcc main.c chttp.c -o example -Wfatal-errors -lws2_32
 
 clean:
 	rm chttp.c chttp.h