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_server.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+
+import pathlib
+import sys
+
+sys.path.append(str(pathlib.Path(__file__).resolve().parents[1]))
+
+from ci_workflow import EnvArg
+from ci_utils import require_env, write_github_output
+from release_workflow import build_release_steps, run_release_workflow
+
+
+def determine_build_targets_step() -> None:
+    import os
+
+    require_env(["EVENT_NAME"])
+    if os.environ["EVENT_NAME"] == "workflow_dispatch":
+        write_github_output({"server": os.environ.get("BUILD_SERVER_INPUT", "")})
+        return
+    write_github_output({"server": "true"})
+
+
+EXTRA_ENV_ARGS = [
+    EnvArg("--event-name", "EVENT_NAME"),
+    EnvArg("--build-server-input", "BUILD_SERVER_INPUT"),
+]
+
+STEPS = build_release_steps(
+    title="Fluxer Server release",
+    image_name_env="IMAGE_NAME_SERVER",
+    extra_steps={"determine_build_targets": determine_build_targets_step},
+)
+
+
+def main() -> int:
+    return run_release_workflow(
+        title="Fluxer Server release",
+        image_name_arg="--image-name-server",
+        image_name_env="IMAGE_NAME_SERVER",
+        extra_steps={"determine_build_targets": determine_build_targets_step},
+        extra_env_args=EXTRA_ENV_ARGS,
+    )
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())