style: dark stealth theme with teal/burgundy pieces and cache-busting

Darken the DaisyUI theme and game board colors for a muted, low-chroma
aesthetic. Pieces use dark teal vs burgundy for subtle contrast.
Add MD5-based cache busting to the DaisyUI stylesheet link so CSS
changes are picked up without a hard refresh.

main.go

@@ -2,8 +2,10 @@ package main
 
 import (
 	"context"
+	"crypto/md5"
 	"database/sql"
 	_ "embed"
+	"encoding/hex"
 	"log"
 	"net/http"
 	"os"
@@ -32,11 +34,13 @@ var (
 var daisyUICSS []byte
 
 func DaisyUIPlugin(v *via.V) {
+	sum := md5.Sum(daisyUICSS)
+	version := hex.EncodeToString(sum[:4])
 	v.HTTPServeMux().HandleFunc("GET /_plugins/daisyui/style.css", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "text/css")
 		_, _ = w.Write(daisyUICSS)
 	})
-	v.AppendToHead(h.Link(h.Rel("stylesheet"), h.Href("/_plugins/daisyui/style.css")))
+	v.AppendToHead(h.Link(h.Rel("stylesheet"), h.Href("/_plugins/daisyui/style.css?v="+version)))
 }
 
 func port() string {