TASK-072: add unescape_helpers.hpp to noinst_HEADERS in src/Makefile.am

The header was missing from the Autotools dist list, meaning make dist
would omit it from the released tarball and break out-of-tree builds.
All in-tree builds were unaffected (masking the gap). Verified via
make dist + tar tzf that the file now appears in the tarball.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: etr

src/Makefile.am

@@ -29,7 +29,7 @@ libhttpserver_la_SOURCES = string_utilities.cpp webserver.cpp http_utils.cpp fil
 # noinst_HEADERS: shipped in the tarball but NEVER installed under $prefix/include.
 # Detail headers (httpserver/detail/*.hpp) live here so they cannot leak to
 # downstream consumers — the public surface comes in through <httpserver.hpp>.
-noinst_HEADERS = httpserver/string_utilities.hpp httpserver/detail/modded_request.hpp httpserver/detail/http_endpoint.hpp httpserver/detail/body.hpp httpserver/detail/webserver_impl.hpp httpserver/detail/webserver_impl_dispatch.hpp httpserver/detail/connection_state.hpp httpserver/detail/secure_zero.hpp httpserver/detail/http_request_impl.hpp httpserver/detail/resource_hook_table.hpp httpserver/detail/route_entry.hpp httpserver/detail/lambda_resource.hpp httpserver/detail/radix_tree.hpp httpserver/detail/route_cache.hpp httpserver/detail/route_tier.hpp gettext.h
+noinst_HEADERS = httpserver/string_utilities.hpp httpserver/detail/modded_request.hpp httpserver/detail/http_endpoint.hpp httpserver/detail/body.hpp httpserver/detail/webserver_impl.hpp httpserver/detail/webserver_impl_dispatch.hpp httpserver/detail/connection_state.hpp httpserver/detail/secure_zero.hpp httpserver/detail/http_request_impl.hpp httpserver/detail/resource_hook_table.hpp httpserver/detail/route_entry.hpp httpserver/detail/lambda_resource.hpp httpserver/detail/radix_tree.hpp httpserver/detail/route_cache.hpp httpserver/detail/route_tier.hpp httpserver/detail/unescape_helpers.hpp gettext.h
 nobase_include_HEADERS = httpserver.hpp httpserver/body_kind.hpp httpserver/cookie.hpp httpserver/constants.hpp httpserver/create_webserver.hpp httpserver/create_test_request.hpp httpserver/webserver.hpp httpserver/webserver_routes.hpp httpserver/webserver_websocket.hpp httpserver/webserver_hooks.hpp httpserver/websocket_handler.hpp httpserver/http_utils.hpp httpserver/ip_representation.hpp httpserver/file_info.hpp httpserver/http_request.hpp httpserver/http_request_auth.hpp httpserver/http_response.hpp httpserver/http_resource.hpp httpserver/feature_unavailable.hpp httpserver/iovec_entry.hpp httpserver/http_arg_value.hpp httpserver/http_method.hpp httpserver/hook_phase.hpp httpserver/hook_action.hpp httpserver/hook_handle.hpp httpserver/hook_context.hpp
 
 AM_CXXFLAGS += -fPIC -Wall