Add allocation-free web auth parsers

Implement strict origin, cookie, and login JSON parsing with
fail-closed validation and output wiping. Add focused host contract
tests
and document the preparatory 8D.3 parser split.

src/CMakeLists.txt

@@ -35,6 +35,7 @@ idf_component_register(
         "web_ui.c"
         "web_server.c"
         "web_session_store.c"
+        "web_auth_parse.c"
         "web_console.c"
         "wifi_config.c"
         "wifi_manager.c"