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_relay_directory/config/directory.json

@@ -0,0 +1,16 @@
+{
+	"$schema": "../../packages/config/src/ConfigSchema.json",
+	"server": {
+		"host": "0.0.0.0",
+		"port": 8080
+	},
+	"database": {
+		"path": "./data/relays.db"
+	},
+	"health_check": {
+		"interval_ms": 30000,
+		"timeout_ms": 5000,
+		"unhealthy_threshold": 3
+	},
+	"bootstrap_relays": []
+}