Initial commit

Assisted-by: GLM 5.3

internal/web/themes.go

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+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: PolyForm-Noncommercial-1.0.0
+
+package web
+
+import "slices"
+
+// Themes are the colour schemes the admin UI ships, in the order the
+// settings switch lists them. Each scheme takes its values from the
+// stops of the matplotlib colour map of the same name.
+var Themes = []string{"viridis", "plasma", "magma"}
+
+// DefaultTheme is the scheme an account without a choice renders in.
+const DefaultTheme = "viridis"
+
+// ThemeCookie carries the colour scheme across the login screen, where
+// no account is known yet.
+const ThemeCookie = "volumen_admin_theme"
+
+// ValidTheme reports whether the value is a shipped colour scheme.
+func ValidTheme(theme string) bool {
+	return slices.Contains(Themes, theme)
+}