Add brand glyph module and use it on the home favorites grid

The design distinguishes apps by stylized brand glyphs (Notion N,
YouTube ▶, Dribbble dot, X 𝕏, Vercel ▲, Behance Bē, Figma F,
Slack #, GitHub ◯, Linear L, plus reading and news clusters). Add
chrome::brand_glyph with a host → Brand dispatcher so any place that
shows an app icon can route through one helper instead of inventing
fallback initials.

Wire it into the home favorites tile first — tabs whose host matches a
known brand now show the proper glyph; unknown hosts still get the
gradient initial fallback. Tests cover canonical hosts, www/subdomain
normalization, the news/reading clusters, and unknown rejection.

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

@@ -1,3 +1,4 @@
+pub(crate) mod brand_glyph;
 pub(crate) mod command_overlay;
 pub(crate) mod home;
 pub(crate) mod settings_layout;
@@ -7,6 +8,7 @@ pub(crate) mod split_pane;
 pub(crate) mod topbar;
 pub(crate) mod wallpaper;
 
+pub(crate) use brand_glyph::render_glyph_for;
 pub(crate) use command_overlay::render_command_overlay;
 pub(crate) use home::render_home_page;
 pub(crate) use settings_layout::render_settings_landing;