Add Typed Display Settings Administration

Implements admin-only Display settings with generation-checked
Apply, Save, Load, Defaults, and Reset operations across the web UI,
CLI, SSH dispatcher, and local UI owner. Adds bounded HTTP handling,
session-isolated operation results, browser lifecycle support, and
comprehensive host tests and documentation.

src/CMakeLists.txt

@@ -34,6 +34,7 @@ idf_component_register(
         "web_serial_settings.c"
         "web_account_settings.c"
         "web_network_settings.c"
+        "web_display_settings.c"
         "web_admin_tickets.c"
         "web_admin_transport.c"
         "web_assets_data.c"