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/.gitignore

@@ -0,0 +1,95 @@
+*.tsbuildinfo
+**/*.beam
+**/*.css.d.ts
+**/*.dump
+**/dump.rdb
+**/*.iml
+**/*.log
+**/*.o
+**/*.plt
+**/*.source
+**/*.swo
+**/*.swp
+**/*.tmp
+**/*~
+**/.*cache
+**/.cache
+**/__pycache__
+**/.dev-runner/
+**/.devenv
+.devenv.flake.nix
+devenv.local.nix
+**/.direnv
+/dev/livekit.yaml
+/dev/bluesky_oauth_key.pem
+/dev/meilisearch_master_key
+/dev/data/
+**/.dev.vars
+**/.DS_Store
+**/.env
+**/.env.*.local
+**/.env.local
+**/.erlang.cookie
+**/.eunit
+**/.idea
+**/.next
+**/.next/cache
+**/.pnp
+**/.pnp.js
+**/.pnpm-store
+**/.rebar
+**/.rebar3
+**/.source
+**/.swc
+**/.turbo
+**/.vercel
+**/_build
+**/_checkouts
+**/_vendor
+**/certificates
+**/coverage
+**/dist
+**/ebin
+**/erl_crash.dump
+**/fluxer.env
+**/generated
+**/log
+**/logs
+**/node_modules
+**/npm-debug.log*
+**/out
+**/pnpm-debug.log*
+**/rebar3.crashdump
+**/secrets.env
+**/target
+**/test-results.json
+**/Thumbs.db
+**/yarn-debug.log*
+**/yarn-error.log*
+/.devserver-cache.json
+**/.devserver-cache.json
+/.fluxer/
+/config/config.json
+/fluxer_app/src/assets/emoji-sprites/
+/fluxer_app/src/components/uikit/AvatarStatusGeometry.ts
+/fluxer_app/src/components/uikit/SVGMasks.tsx
+/fluxer_app/src/locales/*/messages.js
+/fluxer_app/src/locales/*/messages.mjs
+/fluxer_app/src/locales/*/messages.ts
+/fluxer_admin/public/static/app.css
+/fluxer_gateway/config/sys.config
+/fluxer_gateway/config/vm.args
+/fluxer_marketing/public/static/app.css
+/fluxer_server/data/
+/packages/admin/public/static/app.css
+/packages/marketing/public/static/app.css
+/packages/config/src/ConfigSchema.json
+/packages/config/src/MasterZodSchema.generated.tsx
+AGENTS.md
+CLAUDE.md
+fluxer.yaml
+GEMINI.md
+geoip_data
+next-env.d.ts
+.github/agents
+.github/prompts