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.

docs/screen-sharing.md

@@ -28,8 +28,9 @@ Use a Wayland screen-sharing or recording source in your application. Ferese
 opens a display picker. Select a display and press **Share**. Nothing is selected
 by default. Applications that request multiple displays can share up to four.
 The picker uses your Ferese theme colors, font, and shell corner radius. Its
-background follows `theme.material.style`: opaque in solid mode, or translucent
-using the shared **Appearance → Shell opacity** setting (`theme.material.opacity`). Text and icons remain opaque.
+background uses the same compositor material as popovers and authentication
+prompts: opaque in solid mode, or blurred and translucent using the shared
+**Appearance → Shell opacity** and blur settings. Text and icons remain opaque.
 
 Other applications keep a **screen sharing** window with a **Stop sharing** button.
 Ferese’s built-in recorder uses the top-bar stop control instead, leaving your