perf(load-tests): run K6 baseline and fix search.js URLSearchParams bug

- Fix search.js: replace URLSearchParams (unsupported in K6) with string interpolation
- Add baseline performance report with latency benchmarks across all 4 suites
- Add load-tests/results/*.json to .gitignore (large raw output files)

Note: pre-existing test failure in create-listing.handler.spec.ts (eventBus.publish mock) — unrelated to this change.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

load-tests/scripts/search.js

@@ -50,13 +50,9 @@ export default function () {
   if (iter % 2 === 0) {
     // Full-text search
     const query = TEXT_QUERIES[iter % TEXT_QUERIES.length];
-    const params = new URLSearchParams({
-      q: query,
-      limit: '20',
-      offset: '0',
-    });
+    const url = `${BASE_URL}/search?q=${encodeURIComponent(query)}&limit=20&offset=0`;
 
-    const res = http.get(`${BASE_URL}/search?${params.toString()}`, {
+    const res = http.get(url, {
       tags: { name: 'GET /search (text)' },
     });
 
@@ -71,14 +67,9 @@ export default function () {
   } else {
     // Geo search
     const geo = GEO_SEARCHES[iter % GEO_SEARCHES.length];
-    const params = new URLSearchParams({
-      lat: String(geo.lat),
-      lng: String(geo.lng),
-      radius: String(geo.radius),
-      limit: '20',
-    });
+    const url = `${BASE_URL}/search/geo?lat=${geo.lat}&lng=${geo.lng}&radius=${geo.radius}&limit=20`;
 
-    const res = http.get(`${BASE_URL}/search/geo?${params.toString()}`, {
+    const res = http.get(url, {
       tags: { name: 'GET /search/geo' },
     });