Phase 3: Svelte 5 UI skeleton

Svelte 5 + Vite + TypeScript dashboard that consumes kamado-api over
REST for the first paint and then subscribes to /api/ws for live
updates. Zero runtime deps beyond svelte itself; plain CSS, no
component library.

Layout:

- Header with brand, WebSocket status badge, chain + height
- PoolOverview: hashrate (1m/5m/1h/24h), miner count, network
  hashrate + diff, pool share (ppb), expected time to block, uptime
- BlocksTable: recent solves from the in-memory ring (will be
  SQLite-backed in Phase 2b.5)
- BestShares: top-10 workers by bestever, falling back to bestdiff
  when the ckpool patch isn't present
- MinersTable: joined view of stratum clients and workers with
  user-agent-based hardware detection (Bitaxe, NerdQAxe, Antminer,
  ...), hashrate, best-round, best-ever, last share

State is a single $state() snapshot store in svelte-runes form;
components read from it via $derived. The store does one initial
REST snapshot fetch, then owns the WebSocket with exponential
backoff reconnects.

Vite dev server on :5173 proxies /api and /api/ws to localhost:8080
so you can run `make ui-dev` alongside `make up` in development.
Production serving (bundled into the Go binary via embed, behind /
on :8080) lands in Phase 4.

ui/vite.config.ts

@@ -0,0 +1,25 @@
+import { defineConfig } from "vite";
+import { svelte } from "@sveltejs/vite-plugin-svelte";
+
+// Dev server proxies /api (REST and WebSocket) to the running
+// kamado-api container on localhost:8080. In production the Go
+// server serves the built static files alongside /api itself, so
+// there is nothing to proxy.
+export default defineConfig({
+  plugins: [svelte()],
+  server: {
+    port: 5173,
+    proxy: {
+      "/api": {
+        target: "http://localhost:8080",
+        ws: true,
+        changeOrigin: false,
+      },
+    },
+  },
+  build: {
+    outDir: "dist",
+    emptyOutDir: true,
+    target: "es2022",
+  },
+});