refactor: consolidate nvim crates, extract server library, and update workspace dependencies

mcp-memory-nvim/src/main.rs

@@ -0,0 +1,6 @@
+fn main() {
+    let rt = tokio::runtime::Runtime::new().unwrap();
+    rt.block_on(async {
+        nvim_core::run_mcp_loop("mcp-memory-nvim", env!("APP_VERSION")).await;
+    });
+}