fix: use relative Vite base; serve SPA at both /v2/ and /clawstor/

Vite base: '/clawstor/' caused 404s when the SPA was served at /v2/
because asset paths like /clawstor/assets/... didn't match the actual
serve path /v2/assets/...

- vite.config.ts: switch to base: './' (relative paths work from any
  mount point — /v2/, /clawstor/, or bare /)
- serve.rs: mount the SPA at both /v2/ and /clawstor/; add 308 redirect
  from /v2 and /clawstor (no trailing slash) to their canonical forms
  so browsers don't misinterpret the last segment as a filename and
  break relative ./assets/ resolution

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

claw-store/src/serve.rs

@@ -719,12 +719,23 @@ pub fn build_app_with_v2(
         v2_router = v2_router.merge(crate::serve_v2::build(v2s));
     }
     if let Some(dir) = v2_static_dir {
-        v2_router = v2_router.nest_service(
-            "/v2",
-            tower_http::services::ServeDir::new(&dir).fallback(
-                tower_http::services::ServeFile::new(dir.join("index.html")),
-            ),
-        );
+        // Redirect bare paths (no trailing slash) to their canonical
+        // slash-terminated form. Without this, browsers treat the path
+        // segment as a file and resolve relative asset paths one level
+        // too high, producing 404s for `./assets/…`.
+        let redirect_v2 = get(|| async {
+            axum::response::Redirect::permanent("/v2/")
+        });
+        let redirect_clawstor = get(|| async {
+            axum::response::Redirect::permanent("/clawstor/")
+        });
+        let spa = tower_http::services::ServeDir::new(&dir)
+            .fallback(tower_http::services::ServeFile::new(dir.join("index.html")));
+        v2_router = v2_router
+            .route("/v2", redirect_v2)
+            .route("/clawstor", redirect_clawstor)
+            .nest_service("/v2/", spa.clone())
+            .nest_service("/clawstor/", spa);
     }
 
     Router::new()