Refactor theme onto bread-theme; add bakery.toml and release workflow

- breadbox/Cargo.toml: depend on bread-theme with gtk feature
- breadbox/src/main.rs: remove local Palette + hex_to_rgba; use
  bread_theme::{load_palette, hex_to_rgba, gtk::apply_user_css}
- bakery.toml: describes breadbox for bakery install
- release.yml: builds on hestia self-hosted runner, publishes binaries to
  dl.breadway.dev and GitHub Releases on v* tags

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bakery.toml

@@ -0,0 +1,18 @@
+name = "breadbox"
+description = "App launcher for Hyprland / Wayland"
+binaries = ["breadbox", "breadbox-sync"]
+system_deps = ["gtk4", "gtk4-layer-shell", "librsvg"]
+bread_deps = []
+
+[[service]]
+unit = "breadbox-sync.service"
+enable = true
+
+[config]
+dir = "~/.config/breadbox"
+example = "config.example.toml"
+
+[install]
+post_install = [
+    "systemctl --user start breadbox-sync.service 2>/dev/null || breadbox-sync",
+]