refactor(desktop): regroup Settings navigation by user task

[Astro-Han]

Follow-up to #1490. Related tracker: #1303.

Goal

Regroup the existing 14 Settings destinations by user task without changing any destination id, route, persisted selection, command, or page content.

Target groups:

1. General — General, Appearance
2. AI & Work — Models, Memory, Daily Review, Voice
3. Connections — Open Gateway, Remote Access, Web Search
4. System — Usage, Data, Permissions, Health, About

Scope

• Extend SettingsNavGroup and the governed group order to include Connections.
• Update group labels and descriptions in both locales.
• Move existing nav items to the target groups.
• Correct the Appearance destination description: interface language now belongs to General.
• Preserve all 14 SettingsSection ids and current page order within each target group.

Compatibility

• Keep maka-settings-section-v1 values valid.
• Keep settings:<section-id> command-palette ids and actions unchanged.
• Keep requestedSection, OAuth section jumps, direct shell entry points, and retired-id migrations unchanged.
• Do not introduce a new navigation persistence schema.

Acceptance

• The sidebar renders the four target groups and exact membership above.
• All 14 destinations remain enabled and reachable.
• Existing persisted selections open the same page after the regroup.
• The command palette still exposes exactly one command per destination.
• Direct entry points to Models, Memory, Health, and About still reach the same ids.
• English and Chinese group copy and the Appearance description match the final ownership.
• Focus order, keyboard navigation, and narrow Settings sidebar behavior do not regress.
• Focused contracts lock group membership, group order, id stability, command count, and persisted-section compatibility.

Non-goals

• No page merge, removal, or new destination.
• No Settings content redesign.
• No row, section, async-state, or responsive primitive work; that remains in refactor(ui): unify the Settings composition grammar #1360 and the page-group issues.
• No module-subpage work from [Tracking] Module subpage polish — simplify the component vocabulary #1452.

[Astro-Han]

Delivered by #1733, which groups Settings navigation by user task. The proposed Connections group is moot since #1709 removed Open Gateway.