Reduce egress costs, add PWA support, fix Polymarket and Railway relay

Egress optimization:
- Add s-maxage + stale-while-revalidate to all API endpoints for Vercel CDN caching
- Add vercel.json with immutable caching for hashed assets
- Add gzip compression to sidecar responses >1KB
- Add gzip to Railway RSS responses (4 paths previously uncompressed)
- Increase polling intervals: markets/crypto 60s→120s, ETF/macro/stablecoins 60s→180s
- Remove hardcoded Railway URL from theater-posture.js (now env-var only)

PWA / Service Worker:
- Add vite-plugin-pwa with autoUpdate strategy
- Cache map tiles (CacheFirst), fonts (StaleWhileRevalidate), static assets
- NetworkOnly for all /api/* routes (real-time data must be fresh)
- Manual SW registration (web only, skip Tauri)
- Add offline fallback page
- Replace manual manifest with plugin-generated manifest

Polymarket fix:
- Route dev proxy through production Vercel (bypasses JA3 blocking)
- Add 4th fallback tier: production URL as absolute fallback

Desktop/Sidecar:
- Dual-backend cache (_upstash-cache.js): Redis cloud + in-memory+file desktop
- Settings window OK/Cancel redesign
- Runtime config and secret injection improvements

vercel.json

@@ -0,0 +1,34 @@
+{
+  "headers": [
+    {
+      "source": "/assets/(.*)",
+      "headers": [
+        { "key": "Cache-Control", "value": "public, max-age=31536000, immutable" }
+      ]
+    },
+    {
+      "source": "/favico/(.*)",
+      "headers": [
+        { "key": "Cache-Control", "value": "public, max-age=604800" }
+      ]
+    },
+    {
+      "source": "/offline.html",
+      "headers": [
+        { "key": "Cache-Control", "value": "public, max-age=86400" }
+      ]
+    },
+    {
+      "source": "/sw.js",
+      "headers": [
+        { "key": "Cache-Control", "value": "public, max-age=0, must-revalidate" }
+      ]
+    },
+    {
+      "source": "/manifest.webmanifest",
+      "headers": [
+        { "key": "Cache-Control", "value": "public, max-age=86400" }
+      ]
+    }
+  ]
+}