build: add vosk link search to jarvis-gui build.rs

Workspace feature unification pulls vosk into jarvis-gui through
jarvis-core, so jarvis-gui needs the same rustc-link-search as
jarvis-app and jarvis-cli for libvosk.lib at link time.

crates/jarvis-gui/build.rs

@@ -1,4 +1,9 @@
 fn main() {
-    // Tauri build
+    let manifest_dir = std::env::var("CARGO_MANIFEST_DIR").unwrap();
+    let lib_path = std::path::Path::new(&manifest_dir)
+        .join("..\\..\\lib\\windows\\amd64");
+
+    println!("cargo:rustc-link-search=native={}", lib_path.display());
+
     tauri_build::build()
 }