feat: sing-box Clash template support + Docker CI + frontend scaffold

- Clash→sing-box template conversion engine (singbox_template.go)
- Auto-map 40+ Clash rule-providers to sing-box .srs binary rule-sets
- Fix sing-box 1.11+/1.12+ migrations (sniff/block/WireGuard/DNS/rule_set)
- Fix WireGuard URI '+' parsing bug (rawParamGet)
- Add REJECT block outbound for selector group references
- Skip rules referencing rule-sets with no sing-box equivalent
- Verified: sing-box run succeeds with ACL4SSR template (16 rule-sets loaded)
- Add Dockerfile (multi-stage Go build)
- Add GitHub Actions workflow (multi-arch: amd64+arm64, push to ghcr.io)
- Add frontend scaffold (Vue3 + Vite + Tailwind)

frontend/postcss.config.js

@@ -0,0 +1,6 @@
+export default {
+  plugins: {
+    tailwindcss: {},
+    autoprefixer: {},
+  },
+}