Drop 'unsafe-inline' from the Content-Security-Policy (closes #530)

The delete prompts on the webhook page were inline onsubmit handlers.
Each delete form now carries its question in a data-confirm attribute,
which one submit listener in static/js/app.js asks. The three style
attributes became Tailwind classes, with tailwind.css regenerated, and
the x-cloak rule moved to style.css. The policy now sends
script-src 'self' and style-src 'self'.

The browser test now answers a target's delete prompt no and then yes,
and also loads the sign-in page, the webhook list, the settings and
profile pages and the 404 error page under the policy. The README
states the policy as sent.

Model: opus-5-5

internal/server/alpine_browser_test.go

@@ -60,8 +60,8 @@ const (
 // TestAlpineRunsUnderTheSecurityPolicy loads the webhook page and the
 // event log in a headless browser, served by the real router and so
 // under the real Content-Security-Policy, and checks that the pages'
-// Alpine.js directives and the copy control work, and that a target's
-// row shows its delivery counts.
+// Alpine.js directives, the copy control and the delete prompts work,
+// and that a target's row shows its delivery counts.
 func TestAlpineRunsUnderTheSecurityPolicy(t *testing.T) {
 	t.Parallel()
 
@@ -74,6 +74,10 @@ func TestAlpineRunsUnderTheSecurityPolicy(t *testing.T) {
 	userID, _ := env.seedUser(t, "browser", "browser-password")
 	webhook, older, event, target := seedBrowserWebhook(t, env, userID)
 
+	// The sign-in page is loaded before the browser signs in, since a
+	// signed-in visit to it is sent on to another page.
+	checkOtherPages(ctx, t, srv.URL+"/pages/login")
+
 	require.NoError(t, chromedp.Run(
 		ctx, setCookies(srv.URL, env.authCookies(t, userID, "browser")),
 	))
@@ -99,6 +103,11 @@ func TestAlpineRunsUnderTheSecurityPolicy(t *testing.T) {
 	checkEventLog(ctx, t, page+"/events", event.ID, older.ID, target.Name)
 	checkMobileMenu(ctx, t, page)
 	checkPhoneWidth(ctx, t, page, page+"/events", target.Name)
+	checkOtherPages(ctx, t,
+		srv.URL+"/hooks", srv.URL+"/settings", srv.URL+"/user/browser",
+		// A path that does not exist, which gets the 404 error page.
+		srv.URL+"/no-such-page")
+	checkDeletePrompt(ctx, t, page, target)
 
 	assert.Empty(t, problems(), "the browser reported problems")
 }
@@ -1388,3 +1397,75 @@ func checkPhoneWidth(
 	assert.False(t, sideways, "the event log scrolls sideways on a phone")
 	assert.Empty(t, cutOff, "the event log cuts these off on a phone")
 }
+
+// checkOtherPages loads the pages at urls, which no other check opens,
+// so that anything the browser reports going wrong on them fails the
+// test too.
+func checkOtherPages(ctx context.Context, t *testing.T, urls ...string) {
+	t.Helper()
+
+	for _, url := range urls {
+		require.NoError(t, chromedp.Run(ctx, loadPage(url)))
+	}
+}
+
+// answerPrompt returns a script that stands in for the user at the
+// browser's prompt: it makes window.confirm record the question in
+// window.asked and give answer. It also records in window.sent whether
+// a form is sent once its submit event is handled, from a listener on
+// window, which the event reaches after the listener static/js/app.js
+// adds to document.
+func answerPrompt(answer bool) string {
+	return fmt.Sprintf(`
+		window.asked = "";
+		window.sent = false;
+		window.confirm = (question) => {
+			window.asked = question;
+			return %t;
+		};
+		window.addEventListener("submit", (event) => {
+			window.sent = !event.defaultPrevented;
+		});`, answer)
+}
+
+// checkDeletePrompt loads a webhook page and clicks Delete beside
+// target. It checks that the browser asks first, naming the target,
+// that answering no leaves the form unsent, and that answering yes
+// sends it and the target is deleted.
+func checkDeletePrompt(
+	ctx context.Context, t *testing.T, url string, target *database.Target,
+) {
+	t.Helper()
+
+	form := `form[action$="/targets/` + target.ID + `/delete"]`
+	question := `Delete target "` + target.Name + `"?` + "\n\n" +
+		"Nothing more is delivered to it. " +
+		"Its past deliveries stay in the event log."
+
+	var (
+		asked  string
+		sent   bool
+		listed bool
+	)
+
+	require.NoError(t, chromedp.Run(
+		ctx, loadPage(url), chromedp.Evaluate(answerPrompt(false), nil),
+	))
+	click(ctx, t, form+" button")
+	require.NoError(t, chromedp.Run(
+		ctx,
+		chromedp.Evaluate(`window.asked`, &asked),
+		chromedp.Evaluate(`window.sent`, &sent),
+	))
+	assert.Equal(t, question, asked, "Delete does not ask about the target")
+	assert.False(t, sent, "answering no still sends the delete form")
+
+	require.NoError(t, chromedp.Run(
+		ctx, chromedp.Evaluate(answerPrompt(true), nil),
+	))
+	clickAndLoad(ctx, t, form+" button")
+	require.NoError(t, chromedp.Run(ctx, chromedp.Evaluate(
+		`document.querySelector('`+form+`') !== null`, &listed,
+	)))
+	assert.False(t, listed, "answering yes does not delete the target")
+}