Share native theme components and fix dialog backdrop blur

Centralize native palettes, presets, typography, controls, menus, calendar rendering, and icon assets in ferese-theme. Reuse the shared components across the shell, settings, lock screen, authentication prompt, and screen-sharing chooser.

Attach themed dialogs to compositor-owned materials, correct backdrop capture and sampling across output transforms, smooth patterned backgrounds, and prevent clipped picker buttons with the configured shell font.

crates/ferese-theme/assets/icons/status/control-center.svg

@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 60 60" role="img" aria-label="Control center">
+<g transform="translate(0 -4)">
+<rect x="10" y="14" width="40" height="16" rx="8" fill="none" stroke="currentColor" stroke-width="3"/>
+<circle cx="38" cy="22" r="6" fill="#3d7be6"/>
+<rect x="10" y="38" width="40" height="16" rx="8" fill="none" stroke="currentColor" stroke-width="3"/>
+<circle cx="22" cy="46" r="6" fill="currentColor"/>
+</g>
+</svg>