Bump version to 0.3.4: Phase 2 domain cleanup complete

- Split durable Job from transient JobRuntime
- Extracted Schedule value object
- Made RunJob pure (no job mutation)
- Simplified runtime initialization

No observable behavior changes.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/app/version.go

@@ -3,4 +3,4 @@ package app
 // Version is the application version shown in the GUI and used by build
 // scripts in artifact names. It is a var rather than a const so release builds
 // can override it with Go ldflags when CI tags a build.
-var Version = "0.3.3"
+var Version = "0.3.4"