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/GUILD_DELETE.json

@@ -0,0 +1,21 @@
+{
+	"$schema": "https://json-schema.org/draft/2020-12/schema",
+	"name": "GUILD_DELETE",
+	"description": "Sent when a guild becomes unavailable or the user is removed from a guild.",
+	"scope": "guild",
+	"dispatchedBy": ["DELETE /guilds/:guild_id", "DELETE /users/@me/guilds/:guild_id", "gateway"],
+	"payload": {
+		"type": "object",
+		"properties": {
+			"id": {
+				"type": "string",
+				"description": "Guild ID"
+			},
+			"unavailable": {
+				"type": "boolean",
+				"description": "True if the guild is unavailable due to an outage (not a leave/kick)"
+			}
+		},
+		"required": ["id"]
+	}
+}