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/marketing/src/UrlUtils.tsx

@@ -0,0 +1,59 @@
+/*
+ * 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/>.
+ */
+
+/** @jsxRuntime automatic */
+/** @jsxImportSource hono/jsx */
+
+import type {MarketingContext} from '@fluxer/marketing/src/MarketingContext';
+
+export function cacheBustedWithVersion(path: string, version: string): string {
+	const separator = path.includes('?') ? '&' : '?';
+	return `${path}${separator}t=${version}`;
+}
+
+export function cacheBustedAsset(ctx: MarketingContext, path: string): string {
+	return prependBasePath(ctx.basePath, cacheBustedWithVersion(path, ctx.assetVersion));
+}
+
+export function prependBasePath(basePath: string, path: string): string {
+	if (!basePath) return path;
+	return `${basePath}${path}`;
+}
+
+export function href(ctx: MarketingContext, path: string): string {
+	return prependBasePath(ctx.basePath, path);
+}
+
+export function apiUrl(ctx: MarketingContext, path: string): string {
+	return `${ctx.apiEndpoint}${path}`;
+}
+
+export function isCanary(ctx: MarketingContext): boolean {
+	return ctx.releaseChannel === 'canary';
+}
+
+export function normalizeBasePath(basePath: string): string {
+	const segments = basePath
+		.trim()
+		.split('/')
+		.filter((segment) => segment.length > 0);
+
+	if (segments.length === 0) return '';
+	return `/${segments.join('/')}`;
+}