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

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

solitaire_core/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name    = "solitaire_core"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+serde     = { workspace = true }
+chrono    = { workspace = true }
+thiserror = { workspace = true }
+rand      = { workspace = true }

solitaire_core/src/lib.rs

@@ -0,0 +1 @@
+// Game logic modules are added in Phase 2.