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

internal/api/types.go

@@ -0,0 +1,72 @@
+package api
+
+import "havenllo/internal/domain"
+
+type createListRequest struct {
+	Name     string   `json:"name"`
+	Position *float64 `json:"position,omitempty"`
+}
+
+type updateListRequest struct {
+	Name     *string  `json:"name,omitempty"`
+	Position *float64 `json:"position,omitempty"`
+}
+
+type createCardRequest struct {
+	Title       string   `json:"title"`
+	Description string   `json:"description"`
+	Position    *float64 `json:"position,omitempty"`
+}
+
+type updateCardRequest struct {
+	Title       *string  `json:"title,omitempty"`
+	Description *string  `json:"description,omitempty"`
+	Done        *bool    `json:"done,omitempty"`
+	ListID      *int64   `json:"list_id,omitempty"`
+	Position    *float64 `json:"position,omitempty"`
+}
+
+type errorResponse struct {
+	Error apiError `json:"error"`
+}
+
+type apiError struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+type listResponse struct {
+	List domain.List `json:"list"`
+}
+
+type listDetailsResponse struct {
+	List  domain.List   `json:"list"`
+	Cards []domain.Card `json:"cards"`
+}
+
+type listSummary struct {
+	ID        int64   `json:"id"`
+	Name      string  `json:"name"`
+	Position  float64 `json:"position"`
+	CardCount int     `json:"card_count"`
+}
+
+type listsResponse struct {
+	Lists []listSummary `json:"lists"`
+}
+type cardResponse struct {
+	Card domain.Card `json:"card"`
+}
+type cardsResponse struct {
+	Cards []domain.Card `json:"cards"`
+}
+
+func listSummaries(lists []domain.List) []listSummary {
+	summaries := make([]listSummary, 0, len(lists))
+	for _, list := range lists {
+		summaries = append(summaries, listSummary{
+			ID: list.ID, Name: list.Name, Position: list.Position, CardCount: list.CardCount,
+		})
+	}
+	return summaries
+}