feat(open-webui): add Open WebUI chat interface

open-webui/.env.example

@@ -0,0 +1,15 @@
+# Copy to .env and fill in. Never commit .env.
+#
+#   cp .env.example .env
+
+# Signs login sessions and encrypts stored secrets. Keep it stable.
+# Generate one with: openssl rand -hex 32
+WEBUI_SECRET_KEY=
+
+# Let every user see every model, without per-model access grants.
+BYPASS_MODEL_ACCESS_CONTROL=true
+
+# Connections seeded on first start; afterwards they are managed in the admin UI.
+# OPENAI_API_BASE_URL=
+# OPENAI_API_KEY=
+# OLLAMA_BASE_URL=