feat: add fluxer upstream source and self-hosting documentation

- Clone of github.com/fluxerapp/fluxer (official upstream)
- SELF_HOSTING.md: full VM rebuild procedure, architecture overview,
  service reference, step-by-step setup, troubleshooting, seattle reference
- dev/.env.example: all env vars with secrets redacted and generation instructions
- dev/livekit.yaml: LiveKit config template with placeholder keys
- fluxer-seattle/: existing seattle deployment setup scripts

fluxer/packages/hono/src/middleware/ErrorHandler.tsx

@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2026 Fluxer Contributors
+ *
+ * This file is part of Fluxer.
+ *
+ * Fluxer is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Fluxer is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Fluxer. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {createErrorHandler as createFluxerErrorHandler} from '@fluxer/errors/src/ErrorHandler';
+import type {Context, ErrorHandler} from 'hono';
+
+export interface ErrorHandlerOptions {
+	includeStack?: boolean;
+	logger?: (error: Error, context: Context) => void;
+	captureException?: (error: Error, context?: Record<string, unknown>) => void;
+}
+
+export function createErrorHandler(options: ErrorHandlerOptions = {}): ErrorHandler {
+	const {includeStack = false, logger, captureException} = options;
+
+	const logError =
+		logger || captureException
+			? (error: Error, context: Context) => {
+					if (logger) {
+						logger(error, context);
+					}
+					if (captureException) {
+						captureException(error, {
+							path: context.req.path,
+							method: context.req.method,
+							status: context.res?.status,
+						});
+					}
+				}
+			: undefined;
+
+	return createFluxerErrorHandler({
+		includeStack,
+		logError,
+	});
+}