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/scripts/ci/workflows/release_relay.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+
+import pathlib
+import sys
+
+sys.path.append(str(pathlib.Path(__file__).resolve().parents[1]))
+
+from release_workflow import build_release_steps, run_release_workflow
+
+
+STEPS = build_release_steps(
+    title="Fluxer Relay release",
+    image_name_env="IMAGE_NAME",
+)
+
+
+def main() -> int:
+    return run_release_workflow(
+        title="Fluxer Relay release",
+        image_name_arg="--image-name",
+        image_name_env="IMAGE_NAME",
+    )
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())