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/local_status_ui.h

@@ -21,6 +21,22 @@ esp_err_t local_status_ui_start(const local_ui_config_t *config);
 esp_err_t local_status_ui_get_config(local_ui_config_t *config);
 esp_err_t local_status_ui_apply_config(const local_ui_config_t *config);
 
+typedef enum {
+    LOCAL_UI_SETTINGS_APPLY, LOCAL_UI_SETTINGS_SAVE, LOCAL_UI_SETTINGS_LOAD,
+    LOCAL_UI_SETTINGS_DEFAULTS, LOCAL_UI_SETTINGS_RESET
+} local_ui_settings_action_t;
+
+/* Zero-wait RAM projection. Generation is nonzero and never wraps. */
+esp_err_t local_status_ui_get_settings(local_ui_config_t *config, uint32_t *generation);
+/* Reserve configuration across storage IO, without holding a critical section.
+ * Zero expected_generation is for canonical unconditional CLI operations only.
+ * Nonzero stale generations return ESP_ERR_INVALID_STATE; contention returns
+ * ESP_ERR_TIMEOUT. Load retains the canonical default fallback. Reset commits
+ * defaults before publishing RAM, so a storage failure needs no RAM rollback.
+ * No display IO occurs here; successful RAM changes signal renderer activity. */
+esp_err_t local_status_ui_update_settings(local_ui_settings_action_t action,
+    uint32_t expected_generation, const local_ui_config_t *config, bool *loaded_defaults);
+
 /* Preserve a manually selected display diagnostic for a bounded interval. */
 void local_status_ui_hold_for_diagnostics(void);