`Supabase` integration page

[davidsbatista]

Once supabase-haystack is published on PyPI, add an integration tile so it appears on the Haystack integrations webpage.

Tasks

• Create integrations/supabase.md with the correct front matter and content
• Add a Supabase logo (supabase.png) to the /logos/ directory

Integration page structure

---
layout: integration
name: Supabase
description: >
  Use Supabase as a vector store, full-text search backend, or file source in
  your Haystack pipelines — powered by pgvector, PGroonga, and Supabase Storage.
toc: true
---

The body should include:

• Installation section (pip install supabase-haystack)
• Usage section covering each available component with a short initialisation example:
  • SupabasePgVectorDocumentStore + SupabasePgvectorEmbeddingRetriever
  • SupabaseGroongaDocumentStore + SupabaseGroongaRetriever
  • SupabaseBucketDownloader
• Pipeline example showing a RAG pipeline using SupabasePgVectorDocumentStore
• License section

Note: SupabaseVectorBucketDocumentStore is experimental (Supabase Vector Buckets are in alpha upstream) and should be omitted from the tile until stable.

References

• Supabase brand assets (logo): https://supabase.com/brand-assets
• See other integration pages (e.g. integrations/pgvector.md) for the expected structure