fix: harden Edge Function notification path per final review

Fixes issues raised by the whole-branch review before merge:

- Critical: the previous migration hardcoded the live production
  functions URL and anon key as the committed default, so every local
  `supabase db reset` silently pointed dev/test triggers at the real
  project. Adding a new migration instead of editing the already-applied
  one (checksum/drift safety), with local dev values as the committed
  default; production values are applied out-of-band, never committed.

- Important: verify_jwt=true plus sending the anon key as a bearer
  token didn't actually stop anyone, since the anon key is public
  (ships in the frontend bundle) — confirmed empirically, a request
  with a valid anon key but no shared secret now gets a real 401.
  Added a random shared secret known only to the database and the
  Edge Functions' secret store.

- Important: notification emails interpolated raw contact fields into
  HTML with no escaping. Added escapeHtml() and tests proving injected
  markup renders as literal text, not live markup.

- Important: the URL/key/secret functions moved from public to a
  private schema with EXECUTE revoked from anon/authenticated, closing
  an unintended PostgREST RPC endpoint (verified 404 after the fix).

Also adds a test:functions npm script now that Deno is confirmed
available and the shared email builders' tests pass (12 total incl.
the new escaping cases).

Claude-Session: https://claude.ai/code/session_01NhxA4npAXAxmCDEJt6kxSH

supabase/migrations/20260812000001_harden_notify_config.sql

@@ -0,0 +1,112 @@
+-- Follow-up to 20260808000003, prompted by final whole-branch review before
+-- merge. Two problems with the previous migration's approach:
+--
+-- 1. It hardcoded the LIVE PRODUCTION base URL and anon key as the committed
+--    default. Migrations replay on every `supabase db reset`, so any local
+--    dev/test run was silently wired to the live project — once a Resend key
+--    is configured, local testing would send real emails to Mira's inbox
+--    with test data. Fixed by making the committed default the LOCAL dev
+--    values again; production values are applied out-of-band (see below),
+--    never committed.
+--
+-- 2. `verify_jwt = true` + sending the (public) anon key as a bearer token
+--    does not actually stop an attacker: the anon key already ships in the
+--    deployed frontend bundle, so anyone can copy it and POST directly to
+--    the function URLs to trigger arbitrary outbound emails. Fixed by
+--    adding a real shared secret (`edge_functions_notify_secret()`), known
+--    only to this database and the Edge Functions' secret store, checked by
+--    both functions before doing any work.
+--
+-- Both new base-url/anon-key/secret functions move to a `private` schema
+-- (not exposed via PostgREST — only `public` is listed under `[api]` in
+-- config.toml) with EXECUTE explicitly revoked from anon/authenticated, so
+-- they can never become an anon-callable RPC endpoint. The previous
+-- `public.edge_functions_base_url()` / `public.edge_functions_anon_key()`
+-- were reachable that way (POST /rest/v1/rpc/edge_functions_anon_key) —
+-- harmless only because the value itself was already public. Dropped here.
+--
+-- PRODUCTION DEPLOY: after this migration is pushed, apply the real values
+-- out-of-band (never commit these — the anon key is public but the base URL
+-- is project-specific noise, and the notify secret is a genuine secret):
+--
+--   supabase db query --linked "create or replace function private.edge_functions_base_url() returns text language sql immutable as \$\$ select 'https://<project-ref>.supabase.co/functions/v1' \$\$;"
+--   supabase db query --linked "create or replace function private.edge_functions_anon_key() returns text language sql immutable as \$\$ select '<production anon key>' \$\$;"
+--   supabase db query --linked "create or replace function private.edge_functions_notify_secret() returns text language sql immutable as \$\$ select '<random secret>' \$\$;"
+--   supabase secrets set NOTIFY_WEBHOOK_SECRET=<same random secret>
+--   supabase functions deploy on-booking-created
+--   supabase functions deploy on-inquiry-created
+
+create schema if not exists private;
+
+drop function if exists public.edge_functions_base_url();
+drop function if exists public.edge_functions_anon_key();
+
+create or replace function private.edge_functions_base_url()
+returns text
+language sql
+immutable
+as $$
+  select 'http://host.docker.internal:54321/functions/v1'
+$$;
+
+create or replace function private.edge_functions_anon_key()
+returns text
+language sql
+immutable
+as $$
+  select 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJzdXBhYmFzZS1kZW1vIiwicm9sZSI6ImFub24iLCJleHAiOjE5ODM4MTI5OTZ9.CRXP1A7WOeoJeXxjNni43kdQwgnWNReilDMblYTn_I0'
+$$;
+
+-- Local dev placeholder only — production sets a real random value via the
+-- out-of-band command above, never committed to this file.
+create or replace function private.edge_functions_notify_secret()
+returns text
+language sql
+immutable
+as $$
+  select 'local-dev-notify-secret'
+$$;
+
+revoke execute on function private.edge_functions_base_url() from public, anon, authenticated;
+revoke execute on function private.edge_functions_anon_key() from public, anon, authenticated;
+revoke execute on function private.edge_functions_notify_secret() from public, anon, authenticated;
+
+create or replace function public.notify_booking_created()
+returns trigger
+language plpgsql
+security definer
+set search_path = ''
+as $$
+begin
+  perform net.http_post(
+    url := private.edge_functions_base_url() || '/on-booking-created',
+    headers := jsonb_build_object(
+      'Content-Type', 'application/json',
+      'Authorization', 'Bearer ' || private.edge_functions_anon_key(),
+      'X-Notify-Secret', private.edge_functions_notify_secret()
+    ),
+    body := jsonb_build_object('record', to_jsonb(new))
+  );
+  return new;
+end;
+$$;
+
+create or replace function public.notify_inquiry_created()
+returns trigger
+language plpgsql
+security definer
+set search_path = ''
+as $$
+begin
+  perform net.http_post(
+    url := private.edge_functions_base_url() || '/on-inquiry-created',
+    headers := jsonb_build_object(
+      'Content-Type', 'application/json',
+      'Authorization', 'Bearer ' || private.edge_functions_anon_key(),
+      'X-Notify-Secret', private.edge_functions_notify_secret()
+    ),
+    body := jsonb_build_object('record', to_jsonb(new))
+  );
+  return new;
+end;
+$$;