feat: phase 2 widgets — registry, fetchers, clock, config dialog

Backend: internal/widget registry (type metadata + Fetcher), Pi-hole
v5 / AdGuard / Immich fetchers, /api/widgets/types + /api/widgets/:id/data
with 30s TTL cache (failures cached too), kind+config on item create/patch.
Config secrets are never logged or echoed in errors.

Frontend: WidgetContent host maps config.type to a component, polls
/data every 30s for server-backed types; clock renders client-side.
Generic WidgetDialog builds its form from the registry's field list.
Widget tiles are sortable items in both renderers.

Generated with [Devin](https://devin.ai)

Authored By: TDvorak <[email protected]>
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/internal/widget/pihole.go

@@ -0,0 +1,62 @@
+package widget
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// Pi-hole v5 HTTP API: /admin/api.php?summaryRaw&auth=<token>.
+// jarvis: v5 only for now — v6 (/api/...) lands when someone runs it.
+type pihole struct{}
+
+func init() { register(pihole{}) }
+
+func (pihole) Meta() Type {
+	return Type{
+		Type:        "pihole",
+		Name:        "Pi-hole",
+		Description: "Queries and block rate",
+		Fields: []Field{
+			{Key: "endpoint", Label: "Endpoint", Placeholder: "http://pi.hole", Required: true},
+			{Key: "token", Label: "API token", Secret: true, Placeholder: "web password / api token"},
+		},
+	}
+}
+
+type piholeData struct {
+	QueriesToday   int     `json:"queriesToday"`
+	BlockedToday   int     `json:"blockedToday"`
+	BlockedPercent float64 `json:"blockedPercent"`
+	GravitySize    int     `json:"gravitySize"`
+	Status         string  `json:"status"`
+}
+
+func (pihole) Fetch(ctx context.Context, cfg json.RawMessage) (any, error) {
+	endpoint := strings.TrimRight(cfgStr(cfg, "endpoint"), "/")
+	if endpoint == "" {
+		return nil, fmt.Errorf("endpoint required")
+	}
+	u := endpoint + "/admin/api.php?summaryRaw"
+	if tok := cfgStr(cfg, "token"); tok != "" {
+		u += "&auth=" + tok
+	}
+	var raw struct {
+		DNSQueriesToday int     `json:"dns_queries_today"`
+		AdsBlockedToday int     `json:"ads_blocked_today"`
+		AdsPercentToday float64 `json:"ads_percentage_today"`
+		DomainsBlocked  int     `json:"domains_being_blocked"`
+		Status          string  `json:"status"`
+	}
+	if err := getJSON(ctx, u, nil, &raw); err != nil {
+		return nil, err
+	}
+	return piholeData{
+		QueriesToday:   raw.DNSQueriesToday,
+		BlockedToday:   raw.AdsBlockedToday,
+		BlockedPercent: raw.AdsPercentToday,
+		GravitySize:    raw.DomainsBlocked,
+		Status:         raw.Status,
+	}, nil
+}