Split internal/web into subpackages before domain-admin growth.

Lay out view, auth, validate, and handlers under internal/web while keeping
the cmd/panel API unchanged; update roadmap and changelog for web-split closure.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/web/auth/middleware.go

@@ -0,0 +1,45 @@
+package auth
+
+import (
+	"context"
+	"net/http"
+)
+
+type ctxKey int
+
+const usernameKey ctxKey = 0
+
+// RequireAuth wraps a handler so only requests with a valid session cookie
+// reach it; everyone else is redirected to the login page. The authenticated
+// username is stashed in the request context for downstream handlers.
+func (m *Module) RequireAuth(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		token, ok := m.sessionToken(r)
+		if !ok {
+			http.Redirect(w, r, "/login", http.StatusSeeOther)
+			return
+		}
+		username, ok := m.sessions.Lookup(token)
+		if !ok {
+			http.Redirect(w, r, "/login", http.StatusSeeOther)
+			return
+		}
+		if isSessionActivity(r) && m.sessions.Touch(token) {
+			m.setSessionCookie(w, token)
+		}
+		ctx := context.WithValue(r.Context(), usernameKey, username)
+		next.ServeHTTP(w, r.WithContext(ctx))
+	})
+}
+
+func isSessionActivity(r *http.Request) bool {
+	return !(r.Method == http.MethodGet && r.Header.Get("HX-Request") != "")
+}
+
+// CurrentUser returns the authenticated username from the request context.
+func CurrentUser(r *http.Request) string {
+	if v, ok := r.Context().Value(usernameKey).(string); ok {
+		return v
+	}
+	return ""
+}