build(web): add TanStack Query + Testing Library deps

Wires @tanstack/svelte-query for the data layer and
@testing-library/{svelte,jest-dom} for component-level tests. Registers
the jest-dom matchers via a new vitest setup file.

web/package.json

@@ -14,6 +14,8 @@
     "@sveltejs/adapter-static": "^3.0.6",
     "@sveltejs/kit": "^2.8.0",
     "@sveltejs/vite-plugin-svelte": "^4.0.0",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/svelte": "^5.3.1",
     "autoprefixer": "^10.4.20",
     "jsdom": "^25.0.1",
     "postcss": "^8.4.49",
@@ -24,5 +26,8 @@
     "typescript": "^5.6.3",
     "vite": "^5.4.10",
     "vitest": "^2.1.4"
+  },
+  "dependencies": {
+    "@tanstack/svelte-query": "^5.90.2"
   }
 }