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_desktop/packaging/winget/README.md

@@ -0,0 +1,33 @@
+# Fluxer Winget manifest
+
+Windows Package Manager (winget) manifest for installing Fluxer on Windows.
+
+## Placeholders
+
+The `PackageVersion` and `InstallerSha256` fields are set to placeholder values across all three manifest files. Update them before submitting to the winget-pkgs repository.
+
+## Manifest files
+
+- `Fluxer.Fluxer.yaml` -- version manifest (required)
+- `Fluxer.Fluxer.installer.yaml` -- installer details for x64 and arm64
+- `Fluxer.Fluxer.locale.en-US.yaml` -- default locale metadata
+
+## Validating
+
+```bash
+winget validate --manifest .
+```
+
+## Testing locally
+
+```bash
+winget install --manifest .
+```
+
+## Fetching the latest version
+
+```bash
+curl -s https://api.fluxer.app/dl/desktop/stable/win32/x64/latest | jq
+```
+
+This returns a JSON object containing `version`, `pub_date`, and `files` with download URLs and SHA256 checksums for each format.