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/src/presets.rs

@@ -0,0 +1,73 @@
+pub struct Preset {
+    pub name: &'static str,
+    pub description: &'static str,
+    pub accent: &'static str,
+    pub base: &'static str,
+    pub text: &'static str,
+    pub muted: &'static str,
+    pub border: &'static str,
+    pub gradient_end: &'static str,
+}
+
+pub const PRESETS: [Preset; 6] = [
+    Preset {
+        name: "Ferese Blue",
+        description: "Default · logo blue",
+        accent: "#3D7BE6",
+        base: "#111821",
+        text: "#F4F7FB",
+        muted: "#8793A2",
+        border: "#FFFFFF18",
+        gradient_end: "#3D7BE6",
+    },
+    Preset {
+        name: "Monochrome",
+        description: "Dark · grayscale",
+        accent: "#E5E5E5",
+        base: "#101012",
+        text: "#EDEDF0",
+        muted: "#97979F",
+        border: "#FFFFFF18",
+        gradient_end: "#696973",
+    },
+    Preset {
+        name: "Gruvbox",
+        description: "Dark · warm orange",
+        accent: "#FE8019",
+        base: "#282828",
+        text: "#EBDBB2",
+        muted: "#BDAE93",
+        border: "#504945",
+        gradient_end: "#FABD2F",
+    },
+    Preset {
+        name: "Dracula",
+        description: "Dark · purple",
+        accent: "#BD93F9",
+        base: "#282A36",
+        text: "#F8F8F2",
+        muted: "#A4ADCD",
+        border: "#44475A",
+        gradient_end: "#FF79C6",
+    },
+    Preset {
+        name: "Ayu Light",
+        description: "Light · paper",
+        accent: "#8F5300",
+        base: "#F8F9FA",
+        text: "#5C6166",
+        muted: "#596574",
+        border: "#C8CDD3",
+        gradient_end: "#996000",
+    },
+    Preset {
+        name: "Monokai",
+        description: "Dark · warm green",
+        accent: "#A6E22E",
+        base: "#272822",
+        text: "#F8F8F2",
+        muted: "#B2B29F",
+        border: "#414339",
+        gradient_end: "#E6DB74",
+    },
+];