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/mic-mute.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round">
+  <path d="M9 6a3 3 0 0 1 6 0v5M5.5 11.5a6.5 6.5 0 0 0 10.6 5M18.5 11.5a6.5 6.5 0 0 1-.4 2.3M12 18v3m-3 0h6"/>
+  <path d="M4 4l16 16"/>
+</svg>