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_server/tsconfig.json

@@ -0,0 +1,10 @@
+{
+	"extends": "../tsconfigs/hono-service.json",
+	"compilerOptions": {
+		"paths": {
+			"@app/*": ["./src/*"],
+			"@fluxer/*": ["./../packages/*", "./../packages/*/src/index.tsx"]
+		}
+	},
+	"include": ["src/**/*", "../packages/marketing/src/HonoJsx.d.ts"]
+}