Bundle Newsreader serif and apply to hero text

Embeds Newsreader (variable opsz/wght, OFL-licensed) into the
ely_app binary via include_bytes!, registers it through GPUI's
text_system at startup (chrome::typography::register_serif_fonts),
and exposes the SERIF_FAMILY constant for downstream surfaces.

Apply the family to every page hero where the design uses
ely-serif: home headline, settings/appearance headline, plugin
marketplace headline, sync headline, plugin detail name, and the
home reading-list cover headline. The OFL license file ships
alongside the .ttf assets to satisfy the font's redistribution
clause.

crates/ely_app/src/shell/chrome/appearance_form.rs

@@ -9,6 +9,7 @@ use gpui::{
 use gpui_component::{IconName, scroll::ScrollableElement};
 
 use crate::shell::ElyShell;
+use crate::shell::chrome::SERIF_FAMILY;
 
 pub(crate) fn render_appearance_form(
     snapshot: &BrowserSnapshot,
@@ -48,6 +49,7 @@ fn render_header() -> AnyElement {
         )
         .child(
             div()
+                .font_family(SERIF_FAMILY)
                 .text_size(px(34.0))
                 .font_weight(FontWeight(400.0))
                 .text_color(rgb(colors::INK))