feat(server): deliver push without a Firebase project

Every notification depended on Firebase Cloud Messaging, so a missing
Firebase project, which is the current state, meant no notification could be
delivered on any platform. Web Push and token-based Apple Push are now first
class transports alongside FCM, chosen per registered device, and a scheduled
Cloudflare Worker drain retries an outbox so a provider outage delays rather
than drops a message.

server/supabase/functions/_shared/push-contract.test.ts

@@ -3,6 +3,7 @@ import {
   isServiceRoleAuthorization,
   isServiceRoleApiKey,
   parsePushRequest,
+  providerIsSupported,
   PushContractError,
   readFcmConfig,
   sendFcmMessage,
@@ -32,6 +33,12 @@ const fcmConfig = {
   tokenUri: 'https://oauth2.googleapis.com/token',
 }
 
+Deno.test('push providers fcm, webpush, and apns are supported', () => {
+  assert(providerIsSupported('fcm'), 'fcm must be supported')
+  assert(providerIsSupported('webpush'), 'webpush must be supported')
+  assert(providerIsSupported('apns'), 'apns must be supported')
+})
+
 Deno.test('push input accepts only event_type and resource_id', () => {
   const parsed = parsePushRequest({
     event_type: 'transcription.completed',