feat: add edit/delete buttons to list views and inline privacy toggle

Fave cards in the list and profile views now show edit, delete, and
privacy toggle buttons directly — no need to open the detail page first.

- New POST /faves/{id}/privacy route with HTMX privacy toggle partial
- New UpdatePrivacy store method for single-column update
- fave_list.html: edit link, HTMX delete, privacy toggle on every card
- profile.html: edit/delete for owner's own cards
- privacy_toggle.html: new HTMX partial that swaps inline on toggle
- CSS: compact .fave-card-actions styles

The existing handleFaveDelete already returns empty 200 for HTMX
requests, so hx-target="closest article" hx-swap="outerHTML" removes
the card from DOM seamlessly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/handler/fave.go

@@ -335,6 +335,51 @@ func (h *Handler) handleFaveDelete(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, h.deps.Config.BasePath+"/faves", http.StatusSeeOther)
 }
 
+// handleFaveTogglePrivacy toggles a fave's privacy and returns the updated toggle partial.
+func (h *Handler) handleFaveTogglePrivacy(w http.ResponseWriter, r *http.Request) {
+	user := middleware.UserFromContext(r.Context())
+
+	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
+	if err != nil {
+		h.notFound(w, r)
+		return
+	}
+
+	fave, err := h.deps.Faves.GetByID(id)
+	if err != nil {
+		if errors.Is(err, store.ErrFaveNotFound) {
+			h.notFound(w, r)
+			return
+		}
+		slog.Error("get fave error", "error", err)
+		http.Error(w, "Internal error", http.StatusInternalServerError)
+		return
+	}
+
+	if user.ID != fave.UserID {
+		h.forbidden(w, r)
+		return
+	}
+
+	newPrivacy := "private"
+	if fave.Privacy == "private" {
+		newPrivacy = "public"
+	}
+
+	if err := h.deps.Faves.UpdatePrivacy(id, newPrivacy); err != nil {
+		slog.Error("toggle privacy error", "error", err)
+		http.Error(w, "Internal error", http.StatusInternalServerError)
+		return
+	}
+
+	fave.Privacy = newPrivacy
+
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	if err := h.deps.Renderer.Partial(w, "privacy_toggle", fave); err != nil {
+		slog.Error("render privacy toggle error", "error", err)
+	}
+}
+
 // handleTagSearch handles tag autocomplete HTMX requests.
 func (h *Handler) handleTagSearch(w http.ResponseWriter, r *http.Request) {
 	q := r.URL.Query().Get("q")