Include CSS as GResource

Also use explicit namespace for bare functions and constants used in
main.rs.

Cargo.lock

@@ -364,6 +364,15 @@ dependencies = [
  "smallvec",
 ]
 
+[[package]]
+name = "glib-build-tools"
+version = "0.21.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "86aebe63bb050d4918cb1d629880cb35fcba7ccda6f6fc0ec1beffdaa1b9d5c3"
+dependencies = [
+ "gio",
+]
+
 [[package]]
 name = "glib-macros"
 version = "0.21.5"
@@ -1109,6 +1118,7 @@ name = "zoodex"
 version = "1.0.0"
 dependencies = [
  "async-sqlite",
+ "glib-build-tools",
  "gtk4",
  "libadwaita",
  "relm4",