fix(push): "der kommer ikke nogen" kunne ikke besvares

Alt om det var usynligt. Indstillingssiden sagde "til for denne enhed", så snart
der fandtes et abonnement — også når hver eneste push blev afvist. Og en afvist
push gik i en logline på **Debug**, som ikke skrives på en instans, der kører på
standardniveau. Så en levering, der fejler lydløst, og en levering, der aldrig
sker, så ens ud, og forskellen er hele diagnosen.

Tre forskellige problemer havde ét udseende: browseren tilmeldte sig aldrig,
tjenesten afviste den, eller der var ikke noget forfaldent endnu.

**En prøveknap** under Indstillinger → Notifikationer sender én notifikation
gennem den rigtige rute — ikke en genvej, så det, den beviser, er det, der
faktisk skal virke — og siger hvad hver enhed gjorde ved den. Kom den ikke frem,
og afviste ingen den, står der, at det så er browseren eller styresystemet, der
holder den tilbage. Nu peger svaret på ét af de tre steder.

Loglinjen er hævet fra Debug til Warn. Det var den ene linje, der ville have sagt
hvorfor.

Teksten kommer fra klienten, fordi ordbøgerne gør. En server, der bærer sin egen
kopi af "det her er en prøve", bærer den på ét sprog.

**Og en lækage, prøven fandt.** Go pakker en transportfejl som `*url.Error`, og
dens tekst er `Post "https://fcm.googleapis.com/fcm/send/dQw4…": dial tcp: …` —
hele endepunktet, som er den legitimation, push-tjenesten udstedte til den enhed.
Den var på vej ud i svaret, i loglinjen og i ethvert skærmbillede af nogen af dem.
Prøven var skrevet for at bevise, at kun værten blev nævnt, og det var sådan den
blev fundet. Fejlen pakkes ud, og adressen skrubbes bagefter alligevel: den næste
fejltype, der bærer den med, kommer ikke med en advarsel.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/httpapi/notifications_handlers.go

@@ -1,7 +1,9 @@
 package httpapi
 
 import (
+	"errors"
 	"net/http"
+	"net/url"
 	"strings"
 	"time"
 
@@ -106,18 +108,44 @@ func (s *Server) PushToUser(userID, title, body, projectID string) {
 	s.pushToUser(userID, title, body, projectID)
 }
 
-func (s *Server) pushToUser(userID, title, body, projectID string) {
+// pushOutcome is what happened, per device.
+//
+// It exists because "nothing arrives" was unanswerable. A push that a service
+// refuses is the ordinary failure here — a stale subscription, a VAPID subject the
+// service will not take, a browser that revoked permission without telling the
+// server — and every one of them looked exactly like silence.
+type pushOutcome struct {
+	Subscriptions int           `json:"subscriptions"`
+	Sent          int           `json:"sent"`
+	Failed        []pushFailure `json:"failed"`
+}
+
+// pushFailure names the service and quotes what it said.
+//
+// The host and not the endpoint: the rest of that URL is the credential the push
+// service issued for this device, and it does not belong in an answer, a log line
+// or a screenshot.
+type pushFailure struct {
+	Service string `json:"service"`
+	Reason  string `json:"reason"`
+}
+
+func (s *Server) pushToUser(userID, title, body, projectID string) pushOutcome {
 	ctx, cancel := contextWithBackgroundTimeout(30 * time.Second)
 	defer cancel()
 
+	var out pushOutcome
 	subs, err := s.db.ListPushSubscriptions(ctx, userID)
 	if err != nil || len(subs) == 0 {
-		return
+		return out
 	}
+	out.Subscriptions = len(subs)
+
 	public, private, err := s.vapidKeys(ctx)
 	if err != nil {
 		s.log.Warn("vapid keys", "err", err)
-		return
+		out.Failed = append(out.Failed, pushFailure{Service: "verdande", Reason: err.Error()})
+		return out
 	}
 
 	payload := push.Payload{Title: title, Body: body, URL: "/projekt/" + projectID}
@@ -128,13 +156,101 @@ func (s *Server) pushToUser(userID, title, body, projectID string) {
 			Public: public, Private: private, Subject: "mailto:" + s.cfg.SMTP.From,
 		})
 		if err == nil {
+			out.Sent++
 			continue
 		}
-		s.log.Debug("web push failed", "err", err, "endpoint", sub.Endpoint)
+		// Warn, not Debug.
+		//
+		// This was the one line that would have said why no notification ever
+		// arrived, and at Debug it is not printed on an instance running at the
+		// default level. A delivery that fails silently and a delivery that does
+		// not happen look the same from the outside, and the difference is the
+		// whole diagnosis.
+		reason := pushReason(sub.Endpoint, err)
+		s.log.Warn("web push refused", "reason", reason, "service", pushHost(sub.Endpoint), "user", userID)
+		out.Failed = append(out.Failed, pushFailure{
+			Service: pushHost(sub.Endpoint),
+			Reason:  reason,
+		})
 		if recErr := s.db.RecordPushFailure(ctx, sub.Endpoint, push.IsGone(err)); recErr != nil {
 			s.log.Warn("record push failure", "err", recErr)
 		}
 	}
+	return out
+}
+
+// pushReason is what went wrong, with the endpoint taken back out of it.
+//
+// Go wraps a transport failure as `*url.Error`, and its message is `Post
+// "https://fcm.googleapis.com/fcm/send/dQw4w9…": dial tcp: …` — the whole
+// endpoint, which is the credential the push service issued for that device. It
+// would have gone into the answer, the log line and any screenshot of either. A
+// test written to prove the host was reported instead is what found it.
+//
+// Unwrapped first, so the cause is what is quoted. Then the endpoint is scrubbed
+// anyway: the next error type to carry it will not come with a warning.
+func pushReason(endpoint string, err error) string {
+	var urlErr *url.Error
+	if errors.As(err, &urlErr) && urlErr.Err != nil {
+		err = urlErr.Err
+	}
+	reason := err.Error()
+	if endpoint != "" {
+		reason = strings.ReplaceAll(reason, endpoint, pushHost(endpoint))
+	}
+	return reason
+}
+
+// pushHost is the service an endpoint belongs to, and nothing else from it.
+func pushHost(endpoint string) string {
+	u, err := url.Parse(endpoint)
+	if err != nil || u.Host == "" {
+		return "ukendt"
+	}
+	return u.Host
+}
+
+// handlePushTest sends one notification to this account's devices and says what
+// happened to it.
+//
+// Reported as "der kommer ikke nogen". Everything about that was invisible: the
+// settings page said "on for this device" as soon as a subscription existed, and a
+// refusal from the push service went into a Debug line nobody sees. There was no
+// way to tell "the browser never subscribed" from "the service refused it" from
+// "nothing has come due yet" — three different problems with one appearance.
+//
+// It goes through the same path as a real notification rather than a shortcut, so
+// what it proves is the thing that actually has to work.
+//
+// The words come from the client, which is where the dictionaries are. A server
+// that carries its own copy of "This is a test" carries it in one language, and
+// this one deliberately keeps its prose in the interface — see
+// `internal/i18n`. The text is only ever shown back to the person who asked for
+// it, on their own devices.
+func (s *Server) handlePushTest(w http.ResponseWriter, r *http.Request) {
+	var req struct {
+		Title string `json:"title"`
+		Body  string `json:"body"`
+	}
+	if err := decodeJSON(w, r, &req); err != nil {
+		return
+	}
+	title := strings.TrimSpace(req.Title)
+	if title == "" {
+		title = "verdande"
+	}
+	// Bounded: this is written into a notification on somebody's lock screen, and
+	// a megabyte of title is not a notification.
+	if len(title) > 200 {
+		title = title[:200]
+	}
+	body := strings.TrimSpace(req.Body)
+	if len(body) > 500 {
+		body = body[:500]
+	}
+
+	user := userFrom(r.Context())
+	writeJSON(w, http.StatusOK, s.pushToUser(user.ID, title, body, ""))
 }
 
 func (s *Server) vapidKeys(ctx contextLike) (string, string, error) {