Load Alpine's CSP build so the UI's directives run (closes #371)

Every page's Content-Security-Policy forbids eval, which the standard Alpine.js build needs, so no directive ran in a browser: both add forms on the webhook page showed open, and events in the event log could not be collapsed. The UI now loads Alpine's CSP build (@alpinejs/csp 3.14.9 in 3p/); the policy is unchanged. Each directive names a property or method of a component registered in static/js/app.js (collapsible, targetForm), and each card holds its own x-data. A browser test, built only with the browser tag, loads the webhook page and the event log under the real headers; make test-browser runs it in Docker. New test-only dependency chromedp, which raises golang.org/x/sys to 0.47.0.

Model: opus-5-5

go.mod

@@ -4,6 +4,8 @@ go 1.26.1
 
 require (
 	github.com/99designs/basicauth-go v0.0.0-20230316000542-bf6f9cbbf0f8
+	github.com/chromedp/cdproto v0.0.0-20260922220944-a19bff23514f
+	github.com/chromedp/chromedp v0.16.0
 	github.com/dustin/go-humanize v1.0.1
 	github.com/getsentry/sentry-go v0.25.0
 	github.com/go-chi/chi v1.5.5
@@ -29,7 +31,12 @@ require (
 require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/chromedp/sysutil v1.1.0 // indirect
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/go-json-experiment/json v0.0.0-20260820222146-c27c302e5fc3 // indirect
+	github.com/gobwas/httphead v0.1.0 // indirect
+	github.com/gobwas/pool v0.2.1 // indirect
+	github.com/gobwas/ws v1.4.0 // indirect
 	github.com/gorilla/securecookie v1.1.2 // indirect
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/jinzhu/now v1.1.5 // indirect
@@ -50,7 +57,7 @@ require (
 	go.uber.org/zap v1.23.0 // indirect
 	golang.org/x/mod v0.17.0 // indirect
 	golang.org/x/sync v0.14.0 // indirect
-	golang.org/x/sys v0.37.0 // indirect
+	golang.org/x/sys v0.47.0 // indirect
 	golang.org/x/text v0.25.0 // indirect
 	golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d // indirect
 	google.golang.org/protobuf v1.31.0 // indirect