feat(app): bundled Inter and Phosphor icons, window icon

Headings are set in Inter SemiBold, everything else in Inter Regular, so a
title sets the same on every desktop. Media and navigation glyphs (⏭, 🔊, ⛶,
★) come from the Phosphor icon font instead of whichever fallback font had
them. The CJK fallback still loads on its own thread and now joins the
bundled fonts instead of replacing them. The window carries the app icon
on X11 and Windows.

Cargo.lock

@@ -1767,6 +1767,15 @@ dependencies = [
  "unicode-segmentation",
 ]
 
+[[package]]
+name = "egui-phosphor"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "249826f9529c1757d71dbbb3a22ec101b21110ab663c45fb771c2b86121379e4"
+dependencies = [
+ "egui",
+]
+
 [[package]]
 name = "egui-wgpu"
 version = "0.35.0"
@@ -4399,6 +4408,7 @@ dependencies = [
  "directories",
  "eframe",
  "egui",
+ "egui-phosphor",
  "futures",
  "image",
  "parking_lot",