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_docs/schemas/events/VOICE_SERVER_UPDATE.json

@@ -0,0 +1,34 @@
+{
+	"$schema": "https://json-schema.org/draft/2020-12/schema",
+	"name": "VOICE_SERVER_UPDATE",
+	"description": "Sent when the voice server for a guild or call is updated.",
+	"scope": "presence",
+	"dispatchedBy": ["gateway"],
+	"note": "Sent after joining a voice channel or when the voice server changes. Includes channel_id for both guild voice and DM calls.",
+	"payload": {
+		"type": "object",
+		"properties": {
+			"token": {
+				"type": "string",
+				"description": "Voice connection token for authenticating with the voice server"
+			},
+			"endpoint": {
+				"type": "string",
+				"description": "Voice server host (hostname:port)"
+			},
+			"connection_id": {
+				"type": "string",
+				"description": "Connection ID for this voice connection"
+			},
+			"guild_id": {
+				"type": "string",
+				"description": "Guild ID (present for guild voice channels)"
+			},
+			"channel_id": {
+				"type": "string",
+				"description": "Channel ID"
+			}
+		},
+		"required": ["token", "endpoint", "connection_id"]
+	}
+}