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/package.json

@@ -0,0 +1,22 @@
+{
+  "name": "havenllo-web",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc --noEmit && vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "preact": "^10.26.4"
+  },
+  "devDependencies": {
+    "@preact/preset-vite": "^2.10.1",
+    "typescript": "^5.8.3",
+    "vite": "^6.3.5"
+  },
+  "allowScripts": {
+    "esbuild@0.25.12": true
+  }
+}