Add local Supabase backend foundation: schema, RLS, and RLS tests

- supabase/config.toml: local dev stack config, pinned to the app's
  fixed dev server port, email confirmation required (hard
  verification gate per organized-ideas.md).
- Initial schema migration: profiles/roles, the public/private
  catalog tables (manufacturers, device categories, port types, cable
  types, device templates + ports) with the shared is_public/owner_id
  RLS pattern, a generalized catalog_submissions review-queue table,
  and diagrams as JSONB documents (+ collaborators, snapshots) rather
  than fully normalized -- see the migration's header comment for why.
- pgTAP RLS test suite (23 assertions) covering catalog visibility and
  promotion-in-place, diagram owner/collaborator/admin/super-admin
  visibility and edit permissions, submission visibility, and role
  escalation. Caught and fixed a real infinite-recursion bug between
  the diagrams and diagram_collaborators policies before this ever
  touched real data.
- vite.config.ts: pinned dev server port so Supabase Auth's redirect
  allow-list doesn't silently break if Vite floats to another port.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017DUU6CnxECCDeqDNYJgr5x

supabase/.gitignore

@@ -0,0 +1,8 @@
+# Supabase
+.branches
+.temp
+
+# dotenvx
+.env.keys
+.env.local
+.env.*.local