feat(workspace): initialize all seven crates with stubs and blank Bevy window

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

solitaire_engine/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name    = "solitaire_engine"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+bevy            = { workspace = true }
+bevy_egui       = { workspace = true }
+bevy_kira_audio = { workspace = true }
+solitaire_core  = { workspace = true }
+solitaire_data  = { workspace = true }

solitaire_engine/src/lib.rs

@@ -0,0 +1,3 @@
+// Bevy plugins are added in Phase 3.
+// This crate will expose: CardPlugin, TablePlugin, AnimationPlugin,
+// AudioPlugin, UIPlugin, AchievementPlugin, SyncPlugin, GamePlugin.