fix: route all telemetry through edge functions, not PostgREST

- gstack-telemetry-sync: POST to /functions/v1/telemetry-ingest instead of
  /rest/v1/telemetry_events. Removes sed field-renaming (edge function expects
  raw JSONL names). Parses inserted count — holds cursor if zero inserted.
- gstack-update-check: POST to /functions/v1/update-check.
- gstack-community-dashboard: calls community-pulse edge function instead of
  direct PostgREST queries.
- config.sh: removes GSTACK_TELEMETRY_ENDPOINT, fixes misleading comment.

supabase/config.sh

@@ -1,10 +1,8 @@
 #!/usr/bin/env bash
 # Supabase project config for gstack telemetry
 # These are PUBLIC keys — safe to commit (like Firebase public config).
-# RLS policies restrict what the anon/publishable key can do (INSERT only).
+# RLS denies all access to the anon key. All reads and writes go through
+# edge functions (which use SUPABASE_SERVICE_ROLE_KEY server-side).
 
 GSTACK_SUPABASE_URL="https://frugpmstpnojnhfyimgv.supabase.co"
 GSTACK_SUPABASE_ANON_KEY="sb_publishable_tR4i6cyMIrYTE3s6OyHGHw_ppx2p6WK"
-
-# Telemetry ingest endpoint (Data API)
-GSTACK_TELEMETRY_ENDPOINT="${GSTACK_SUPABASE_URL}/rest/v1"