Add manual refresh toggle to dashboard widgets

[multiplex55]

Motivation

• Provide a per-widget option to disable automatic refresh and rely on explicit refreshes to reduce unnecessary updates.
• Expose the control in the shared refresh UI so all widgets can present a consistent setting via refresh_interval_setting.
• Ensure the existing header Refresh button and settings-driven refresh behavior still force an immediate refresh even when auto-refresh is disabled.

Description

• Change refresh_interval_setting to accept a manual_refresh_only: &mut bool parameter and add an "Only manual refresh" checkbox to the settings UI.
• Add a manual_refresh_only: bool field (with #[serde(default)]) to each affected widget config and set the backward-compatible default to false in the Default impls for those configs.
• Add a refresh_pending: bool field to each updated widget and update refresh logic so widgets skip automatic refreshes when manual_refresh_only is true but still perform immediate refreshes on header Refresh or when settings change by using refresh_pending.
• Update the following widget modules: pinned_query_results, query_list, system_actions, system_status, window_list, windows_overview, process_list, and browser_tabs to store and honor the flag and to keep cache interval and invalidation behavior.

Testing

• No automated tests were executed as part of this change.

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Codex Task