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_devops/cassandra/migrations/20251027204850_voice_regions_v2.cql

@@ -0,0 +1,32 @@
+CREATE TABLE IF NOT EXISTS fluxer.voice_regions (
+    id text PRIMARY KEY,
+    name text,
+    emoji text,
+    latitude double,
+    longitude double,
+    priority int,
+    is_default boolean,
+    vip_only boolean,
+    required_guild_features set<text>,
+    allowed_guild_ids set<bigint>,
+    allowed_user_ids set<bigint>,
+    created_at timestamp,
+    updated_at timestamp
+);
+
+CREATE TABLE IF NOT EXISTS fluxer.voice_servers (
+    region_id text,
+    server_id text,
+    endpoint text,
+    api_key text,
+    api_secret text,
+    priority int,
+    is_active boolean,
+    vip_only boolean,
+    required_guild_features set<text>,
+    allowed_guild_ids set<bigint>,
+    allowed_user_ids set<bigint>,
+    created_at timestamp,
+    updated_at timestamp,
+    PRIMARY KEY (region_id, server_id)
+);