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_integration/tsconfig.json

@@ -0,0 +1,13 @@
+{
+	"extends": "../tsconfigs/base.json",
+	"compilerOptions": {
+		"outDir": "./dist",
+		"rootDir": "./src",
+		"types": ["node", "vitest/globals"],
+		"paths": {
+			"@fluxer/integration/*": ["./src/*"]
+		}
+	},
+	"include": ["src/**/*"],
+	"exclude": ["node_modules", "dist"]
+}