build: update golangci-lint to v2.12.2 with commit-pinned installs

Pin golangci-lint to commit c0d3ddc9cf3faa61a4e378e879ece580256d76e5
(v2.12.2) in Dockerfile and script/bootstrap. Fix the goconst findings
the new version reports under the unchanged canonical .golangci.yml by
extracting shared test fixture constants and a statusError constant in
the watcher.

internal/notify/delivery_test.go

@@ -25,6 +25,18 @@ const (
 	colorDefault = "#6c757d"
 )
 
+// Priority and fixture values shared across tests.
+const (
+	prioError   = "error"
+	prioWarning = "warning"
+	prioInfo    = "info"
+	prioSuccess = "success"
+	prioUnknown = "unknown"
+	ntfyUrgent  = "urgent"
+	ntfyDefault = "default"
+	testHost    = "example.com"
+)
+
 // errSimulated is a static error for transport failures.
 var errSimulated = errors.New("simulated transport failure")
 
@@ -101,13 +113,13 @@ func TestNtfyPriority(t *testing.T) {
 		input string
 		want  string
 	}{
-		{"error", "urgent"},
-		{"warning", "high"},
-		{"success", "default"},
-		{"info", "low"},
-		{"", "default"},
-		{"unknown", "default"},
-		{"critical", "default"},
+		{prioError, ntfyUrgent},
+		{prioWarning, "high"},
+		{prioSuccess, ntfyDefault},
+		{prioInfo, "low"},
+		{"", ntfyDefault},
+		{prioUnknown, ntfyDefault},
+		{"critical", ntfyDefault},
 	}
 
 	for _, tc := range cases {
@@ -134,12 +146,12 @@ func TestSlackColor(t *testing.T) {
 		input string
 		want  string
 	}{
-		{"error", colorError},
-		{"warning", colorWarning},
-		{"success", colorSuccess},
-		{"info", colorInfo},
+		{prioError, colorError},
+		{prioWarning, colorWarning},
+		{prioSuccess, colorSuccess},
+		{prioInfo, colorInfo},
 		{"", colorDefault},
-		{"unknown", colorDefault},
+		{prioUnknown, colorDefault},
 		{"critical", colorDefault},
 	}
 
@@ -165,7 +177,7 @@ func TestNewRequest(t *testing.T) {
 
 	target := &url.URL{
 		Scheme: "https",
-		Host:   "example.com",
+		Host:   testHost,
 		Path:   "/webhook",
 	}
 	body := bytes.NewBufferString("hello")
@@ -187,9 +199,9 @@ func TestNewRequest(t *testing.T) {
 		)
 	}
 
-	if req.Host != "example.com" {
+	if req.Host != testHost {
 		t.Errorf(
-			"Host = %q, want %q", req.Host, "example.com",
+			"Host = %q, want %q", req.Host, testHost,
 		)
 	}
 
@@ -217,7 +229,7 @@ func TestNewRequestPreservesContext(t *testing.T) {
 		ctxKey("k"),
 		"v",
 	)
-	target := &url.URL{Scheme: "https", Host: "example.com"}
+	target := &url.URL{Scheme: "https", Host: testHost}
 
 	req := notify.NewRequestForTest(
 		ctx, http.MethodGet, target, http.NoBody,
@@ -289,10 +301,10 @@ func TestSendNtfyHeaders(t *testing.T) {
 		)
 	}
 
-	if captured.priority != "urgent" {
+	if captured.priority != ntfyUrgent {
 		t.Errorf(
 			"Priority header = %q, want %q",
-			captured.priority, "urgent",
+			captured.priority, ntfyUrgent,
 		)
 	}
 
@@ -311,10 +323,10 @@ func TestSendNtfyAllPriorities(t *testing.T) {
 		input string
 		want  string
 	}{
-		{"error", "urgent"},
-		{"warning", "high"},
-		{"success", "default"},
-		{"info", "low"},
+		{prioError, ntfyUrgent},
+		{prioWarning, "high"},
+		{prioSuccess, ntfyDefault},
+		{prioInfo, "low"},
 	}
 
 	for _, tc := range priorities {
@@ -550,11 +562,11 @@ func TestSendSlackAllColors(t *testing.T) {
 		priority string
 		want     string
 	}{
-		{"error", colorError},
-		{"warning", colorWarning},
-		{"success", colorSuccess},
-		{"info", colorInfo},
-		{"unknown", colorDefault},
+		{prioError, colorError},
+		{prioWarning, colorWarning},
+		{prioSuccess, colorSuccess},
+		{prioInfo, colorInfo},
+		{prioUnknown, colorDefault},
 	}
 
 	for _, tc := range colors {