Remove unsafe-inline from the Content-Security-Policy (closes #125)

script-src and style-src now allow only 'self'. The generator page's
two inline onclick handlers, which selected the generated URL and
copied it, move into internal/static/generator.js and are attached
with addEventListener. The bundled Tailwind script, which built styles
in the browser and injected them at runtime, is replaced by a small
hand-written internal/static/style.css holding only the rules the
login and generator pages use; the templates carry a few plain class
names in place of Tailwind's. No build step. The pages keep their
layout, not every pixel of it.

Model: opus-5-5

internal/server/routes.go

@@ -53,7 +53,7 @@ func (s *Server) SetupRoutes() {
 	// Robots.txt
 	s.router.Get("/robots.txt", s.h.HandleRobotsTxt())
 
-	// Static files (Tailwind CSS, etc.)
+	// The login and generator pages' stylesheet and script
 	s.router.Handle("/static/*", http.StripPrefix("/static/", static.Handler()))
 
 	// Login/generator UI. The form routes carry CSRF protection; the