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/fluxer_api/src/App.tsx

@@ -0,0 +1,72 @@
+/*
+ * 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 {Config} from '@app/Config';
+import {shutdownInstrumentation} from '@app/Instrument';
+import {Logger} from '@app/Logger';
+import {createAPIApp} from '@fluxer/api/src/App';
+import {initializeConfig} from '@fluxer/api/src/Config';
+import {initializeLogger} from '@fluxer/api/src/Logger';
+import {isTelemetryActive} from '@fluxer/api/src/Telemetry';
+import {createServer, setupGracefulShutdown} from '@fluxer/hono/src/Server';
+import {setUser} from '@fluxer/sentry/src/Sentry';
+
+async function main(): Promise<void> {
+	initializeConfig(Config);
+	initializeLogger(Logger);
+
+	const {app, initialize, shutdown} = await createAPIApp({
+		config: Config,
+		logger: Logger,
+		setSentryUser: setUser,
+		isTelemetryActive,
+	});
+
+	await initialize();
+
+	process.on('uncaughtException', (error) => {
+		Logger.fatal({error}, 'Uncaught exception');
+		process.exit(1);
+	});
+
+	process.on('unhandledRejection', (reason) => {
+		Logger.fatal({reason}, 'Unhandled rejection');
+		process.exit(1);
+	});
+
+	const server = createServer(app, {port: Config.port});
+
+	Logger.info({port: Config.port}, `Starting Fluxer API on port ${Config.port}`);
+
+	setupGracefulShutdown(
+		async () => {
+			await shutdownInstrumentation();
+			await shutdown();
+			await new Promise<void>((resolve) => {
+				server.close(() => resolve());
+			});
+		},
+		{logger: Logger, timeoutMs: 30000},
+	);
+}
+
+main().catch((err) => {
+	Logger.fatal({error: err}, 'Failed to start Fluxer API');
+	process.exit(1);
+});