Sustainable LibreChat setup: official manifest, config layer, brand overlay

- CloudronManifest.json: byte-identical copy of the OFFICIAL appstore manifest
  (the hand-edited one stripped addons and crash-looped the app on 2026-10-18)
- Dockerfile: pinned base (202610150224320000), brand assets only + title sed
- librechat.yaml: schema 1.3.17; chat models only in picker (qwen-image moved
  to the agent image tool); speech via gateway with capped key refs; SearXNG
  web search; inference-docs MCP server; forward-compatible interface.theme
- mcp/server.py: docs MCP server (stdio, stdlib-only, tool search_docs)
- assets/: co-op logo + favicons/PWA icons

.dockerignore

@@ -0,0 +1,2 @@
+.git
+*.md