ci: pin playwright to 1.61.1 matching runner image

Floating "^1" resolved to 1.61.1 while the e2e container was pinned
to v1.59.0-jammy, so its browser builds were missing at launch. Pin the
dep exact and bump the image so the two versions move together.

package.json

@@ -31,7 +31,7 @@
   },
   "devDependencies": {
     "@biomejs/biome": "^2",
-    "@playwright/test": "^1",
+    "@playwright/test": "1.61.1",
     "@size-limit/preset-small-lib": "^11",
     "@vitest/coverage-v8": "^2",
     "jsdom": "^25",