fix(analytics): proxy PostHog through own domain to bypass ad blockers

- Add /ingest/* rewrites in vercel.json → us.i.posthog.com
- Web uses /ingest proxy, desktop uses direct PostHog host
- Enable capture_pageview so every visitor registers

vercel.json

@@ -1,5 +1,9 @@
 {
   "ignoreCommand": "if [ -z \"$VERCEL_GIT_PREVIOUS_SHA\" ]; then exit 1; fi; git diff --quiet $VERCEL_GIT_PREVIOUS_SHA $VERCEL_GIT_COMMIT_SHA -- api/ src/ server/ proto/ public/ index.html settings.html middleware.ts vite.config.ts vercel.json package.json tsconfig.json data/",
+  "rewrites": [
+    { "source": "/ingest/static/:path*", "destination": "https://us-assets.i.posthog.com/static/:path*" },
+    { "source": "/ingest/:path*", "destination": "https://us.i.posthog.com/:path*" }
+  ],
   "headers": [
     {
       "source": "/",