chore(deps): remove deprecated subscriptions-transport-ws (#2922)

Removes the deprecated `subscriptions-transport-ws` package (Renovate dependency dashboard #49).

The package is unmaintained and was only reachable through the Apollo `WebSocketLink` in `app/plugins/apollo.ts`. The schema has no `Subscription` type and no subscription operations are defined, so the ws `split()` branch was dead code.

- Drop `WebSocketLink`, the `split()` routing, `getMainDefinition`, and `wsUrl` from `app/plugins/apollo.ts`
- Remove the direct `subscriptions-transport-ws` dependency

Verified with `npm run build` (green) and eslint (clean).

Note: the package lingers in the lockfile as an optional peer dep of `@apollo/client` v3; it disappears with the Apollo Client v4 upgrade, which removes `@apollo/client/link/ws` entirely.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #2922

package.json

@@ -58,8 +58,7 @@
     "graphql": "16.14.0",
     "graphql-tag": "2.12.6",
     "pinia": "3.0.4",
-    "pinia-plugin-persistedstate": "4.7.1",
-    "subscriptions-transport-ws": "0.11.0"
+    "pinia-plugin-persistedstate": "4.7.1"
   },
   "engines": {
     "node": "24"