Owner notices: the stall, one webhook path from env to Discord (#171)

Rollout note: the owner_notices table starts empty, so the first pass after deploy sends for conditions already true — correct per one-row-per-episode; say so rather than have it reported as a bug. Prod step: create the webhook, set DISCORD_WEBHOOK_URL on the deployment, redeploy — unset is silent by design, and without that step the feature ships dark. Security invariants preserved: the webhook address is a secret in the class of TOKEN_KEY (never logged, never on a config-printing line), and the owner gate is unchanged.

backend/main_test.go

@@ -21,10 +21,17 @@ func TestLoadLatestPollDefaults(t *testing.T) {
 	}
 }
 
-func TestLoadConfigReadsCoverDirectory(t *testing.T) {
-	t.Setenv("COVER_DIR", "/covers")
-	if got := loadConfig().CoverDir; got != "/covers" {
-		t.Fatalf("CoverDir = %q, want /covers", got)
+func TestLoadConfigReadsDiscordWebhook(t *testing.T) {
+	// The address is read, never defaulted: unset stays empty (the whole
+	// path is off), set flows into the Config for the poller's notifier.
+	const url = "https://discord.com/api/webhooks/000000/secret"
+	t.Setenv("DISCORD_WEBHOOK_URL", url)
+	if got := loadConfig().DiscordWebhookURL; got != url {
+		t.Fatalf("DiscordWebhookURL = %q, want %q", got, url)
+	}
+	t.Setenv("DISCORD_WEBHOOK_URL", "")
+	if got := loadConfig().DiscordWebhookURL; got != "" {
+		t.Fatalf("DiscordWebhookURL = %q, want empty when unset", got)
 	}
 }
 
@@ -51,7 +58,8 @@ func TestLoadLatestPollEnabledParsing(t *testing.T) {
 // nothing here sizes a cooldown any more.
 func TestNewLatestPollerWiresFetchers(t *testing.T) {
 	tls := &latest.TLSFetcher{}
-	p := newLatestPoller(nil, LatestPoll{Enabled: true}, tls, nil)
+	notifier := &stubNotifier{}
+	p := newLatestPoller(nil, LatestPoll{Enabled: true}, tls, nil, notifier)
 	if p.Fetch != tls {
 		t.Fatalf("Fetch not wired")
 	}
@@ -67,8 +75,15 @@ func TestNewLatestPollerWiresFetchers(t *testing.T) {
 	if p.Now == nil {
 		t.Fatalf("Now = nil, want the live clock")
 	}
+	if p.Notify != notifier {
+		t.Fatalf("Notify = %v, want the configured notifier", p.Notify)
+	}
 }
 
+// stubNotifier satisfies latest.Notifier so newLatestPoller's wiring can be
+// asserted; it is never called.
+type stubNotifier struct{ latest.Notifier }
+
 func TestPutStatusValidation(t *testing.T) {
 	cases := []struct {
 		name   string