feat: implement Havenllo single-board kanban (Go+SQLite backend, Preact/Vite frontend)

- Single fixed 'Haven' board: lists (To do/In progress/Done) + cards, no multi-board
- Go 1.24 backend, CGO-free modernc.org/sqlite, embedded SPA, REST /api
- Preact + Vite + TS frontend, native HTML5 drag-and-drop, optimistic UI, dark Haven theme
- PVC (nfs-client) for SQLite, root container on NFS, simple nginx ingress havenllo.haven
- Dockerfile multi-arch build, Gitea CI via pipeline-actions@main

web/vite.config.ts

@@ -0,0 +1,11 @@
+import { defineConfig } from "vite";
+import preact from "@preact/preset-vite";
+
+export default defineConfig({
+  plugins: [preact()],
+  build: {
+    outDir: "dist",
+    emptyOutDir: true
+  }
+});
+