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

- breadpad-shared/Cargo.toml: depend on bread-theme (no gtk feature needed
  in the shared crate)
- breadpad-shared/src/theme.rs: re-export Palette and load_palette from
  bread-theme; retain all breadpad-specific CSS in build_css()
- bakery.toml: describes breadpad for bakery install
- release.yml: builds on hestia self-hosted runner, publishes binaries to
  dl.breadway.dev and GitHub Releases on v* tags

bakery.toml

@@ -0,0 +1,14 @@
+name = "breadpad"
+description = "Quick-capture scratchpad and note viewer with AI classification"
+binaries = ["breadpad", "breadman"]
+system_deps = ["gtk4", "gtk4-layer-shell"]
+bread_deps = []
+
+[config]
+dir = "~/.config/breadpad"
+example = "breadpad.example.toml"
+
+[install]
+post_install = [
+    "mkdir -p ~/.local/share/breadpad/model",
+]