feat: redesign Manage tab to match reference layout

- Add Customization group: User Interface (CUI), Tool Palettes (large),
  Import, Export, Edit Aliases dropdown (small)
- Add Cleanup group: Find Non-Purgeable Items (large), Purge, Overkill, Audit (small)
- Add 8 new SVG icons for all new commands

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/manage/user_interface.rs

@@ -0,0 +1,5 @@
+use crate::modules::{IconKind, ModuleEvent, ToolDef};
+pub const ICON: IconKind = IconKind::Svg(include_bytes!("../../../assets/icons/user_interface.svg"));
+pub fn tool() -> ToolDef {
+    ToolDef { id: "CUI", label: "User\nInterface", icon: ICON, event: ModuleEvent::Command("CUI".to_string()) }
+}