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/packages/number_utils/package.json

@@ -0,0 +1,12 @@
+{
+	"name": "@fluxer/number_utils",
+	"version": "0.0.0",
+	"type": "module",
+	"dependencies": {
+		"@fluxer/constants": "workspace:*"
+	},
+	"exports": {
+		"./src/*": "./src/*",
+		"./*": "./*"
+	}
+}