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

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

Cargo.lock

@@ -302,6 +302,15 @@ dependencies = [
  "piper",
 ]
 
+[[package]]
+name = "bread-theme"
+version = "0.1.0"
+dependencies = [
+ "dirs 5.0.1",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "breadman"
 version = "0.1.0"
@@ -343,6 +352,7 @@ name = "breadpad-shared"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "bread-theme",
  "chrono",
  "dirs 5.0.1",
  "ical",