feat: add org filter dropdown to Dashboard view

Add an org filter select to the dashboard that allows users to narrow
the triage queue to a specific organization. The filter uses HTMX to
update the view without a full page reload, mirroring the pattern
already used in the issues and pulls views.

Closes leeworks-agents/gitea-mobile#68

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

internal/handlers/handlers.go

@@ -188,18 +188,30 @@ func (h *Handler) Dashboard(w http.ResponseWriter, r *http.Request) {
 
 	token := getToken(r)
 	orgs := h.getUserOrgs(r)
+	selectedOrg := r.URL.Query().Get("org")
 
 	type dashboardData struct {
-		Items []giteaclient.TriageItem
-		Error string
+		Items       []giteaclient.TriageItem
+		Orgs        []string
+		SelectedOrg string
+		Error       string
 	}
 
-	var data dashboardData
+	data := dashboardData{
+		Orgs:        orgs,
+		SelectedOrg: selectedOrg,
+	}
 
 	if len(orgs) == 0 {
 		data.Error = "No organizations found. Check your token permissions."
 	} else {
-		queue, err := h.Client.GetTriageQueue(r.Context(), token, orgs)
+		// Determine which orgs to query.
+		queryOrgs := orgs
+		if selectedOrg != "" {
+			queryOrgs = []string{selectedOrg}
+		}
+
+		queue, err := h.Client.GetTriageQueue(r.Context(), token, queryOrgs)
 		if err != nil {
 			slog.Error("failed to get triage queue", "error", err)
 			data.Error = "Error loading triage queue."