chore: add Renovate configuration and workflows

- Introduced .renovaterc for Renovate settings.
- Added renovate.config.cjs for Gitea integration.
- Created .gitea/workflows/renovate.yml for daily Renovate runs.
- Added .gitea/workflows/test.yml for CI testing.
- Removed outdated GitHub workflows and configuration files.

renovate.config.cjs

@@ -0,0 +1,6 @@
+module.exports = {
+	endpoint: "https://code.popov.link",
+	gitAuthor: "renovate[bot] <renovatebot@noreply.localhost>",
+	optimizeForDisabled: true,
+	platform: "gitea",
+};