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_admin/package.json

@@ -0,0 +1,27 @@
+{
+	"name": "fluxer_admin",
+	"private": true,
+	"type": "module",
+	"scripts": {
+		"build:css": "pnpm --filter @fluxer/admin build:css",
+		"build:css:watch": "pnpm --filter @fluxer/admin build:css:watch",
+		"dev": "tsx watch --clear-screen=false src/index.tsx",
+		"start": "tsx src/index.tsx",
+		"typecheck": "tsgo --noEmit"
+	},
+	"dependencies": {
+		"@fluxer/admin": "workspace:*",
+		"@fluxer/config": "workspace:*",
+		"@fluxer/constants": "workspace:*",
+		"@fluxer/hono": "workspace:*",
+		"@fluxer/initialization": "workspace:*",
+		"@fluxer/logger": "workspace:*",
+		"tsx": "catalog:"
+	},
+	"devDependencies": {
+		"@types/node": "catalog:",
+		"@typescript/native-preview": "catalog:",
+		"tailwindcss": "catalog:"
+	},
+	"packageManager": "pnpm@10.29.3"
+}