R9 Web Push, then the honest version: VAPID key, push subscriptions, encrypted pushes, 4.5.0 advertised

The server's VAPID key (PushKeys, made on first need, in Mongo) is the instance API's vapid.public_key and every app's
vapid_key. /api/v1/push/subscription (POST, GET, PUT, DELETE) keeps one subscription per access token, so per persona;
every notification kept (never a filtered one) is queued as a SendPush job for the subscriptions whose alert and policy
admit it, and sent through the `push` client (the safe handler, https only) encrypted as RFC 8291 aes128gcm or the
aesgcm draft with an ES256 VAPID JWT. 404/410 delete the subscription, 429/5xx/timeouts retry, other answers drop the
push. Subscriptions end with their tokens (revocation, sessions ended, suspension, deletion, a restore); backups hold
neither keys nor subscriptions. The walk of every Mastodon 4.3-4.5 client route (docs/MASTODON-API.md) added
conversations/:id/unread, domain_blocks/preview, v2 notifications clear and PUT policy, /oauth/userinfo and stubs, so both
instance APIs now say 4.5.0 (compatible; PrivaPub <release>). The pasture gets a push sink (pushsink.test) and
scenarios/push.sh in batch A.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WpVCoDeM1qUTRp4fXQdfof

PrivaPub/Api/Mastodon/Controllers/NotificationRequestsController.cs

@@ -69,7 +69,7 @@ namespace PrivaPub.Api.Mastodon.Controllers
 		[HttpGet("/api/v2/notifications/policy"), Scope("read:notifications")]
 		public async Task<IActionResult> Policy(CancellationToken token) => Json(await V2(await NotificationPolicies.Of(MyId, token), token));
 
-		[HttpPatch("/api/v2/notifications/policy"), Scope("write:notifications")]
+		[HttpPatch("/api/v2/notifications/policy"), HttpPut("/api/v2/notifications/policy"), Scope("write:notifications")]
 		public async Task<IActionResult> SetPolicy(CancellationToken token)
 		{
 			var policy = await NotificationPolicies.Of(MyId, token);