feat: add Docker support with demo mode and database reset functionality

.dockerignore

@@ -0,0 +1,14 @@
+# SPDX-FileCopyrightText: 2026 Paul Schoeneck
+#
+# SPDX-License-Identifier: AGPL-3.0-only AND LicenseRef-KIBU-Additional-Terms
+
+.git
+.next
+node_modules
+.env
+.env.*
+!.env.example
+!.env.example.license
+*.tsbuildinfo
+test-results
+playwright-report