House rules: numbers through one formatter, no made-up server errors, and the rules fail the build

- Every number shown on a page goes through NumbersExtensions: counts,
  percentages, the nerd readouts and the values written into a style.
- A failure the client builds itself (offline, timeout, retries run out, an
  answer it can't read) is a 400 that names its kind; only a server's own 5XX
  passes through.
- Login, sign-up, recovery and password confirmations leave autocomplete to
  the browser, so it can offer the saved login.
- The Daisy components start with empty lists and attributes, and a
  decorative image still renders alt="".
- Arasaka.HouseRules.Analyzers checks all of this in every build, together
  with PrivaPub.ClientModels.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W4YtEJrgxG12Pc39Fai8Bd

Services/PushService.cs

@@ -112,7 +112,7 @@ namespace decePubClient.Services
 				if (personaIds.Count > 0 && key is null)
 				{
 					await Save(device, cancellationToken);
-					return result.Invalidate(localizer["This server does not offer push notifications."], (int)HttpStatusCode.NotImplemented);
+					return result.Invalidate(localizer["This server does not offer push notifications."], (int)HttpStatusCode.BadRequest);
 				}
 
 				foreach (var personaId in personaIds)
@@ -252,7 +252,7 @@ namespace decePubClient.Services
 				{
 					if (isNew)
 						await Js("unsubscribe", false, [entry.Slot], cancellationToken);
-					return new WebResult().Invalidate(localizer["This browser did not subscribe: {0}", browser?.Error ?? "?"], (int)HttpStatusCode.ServiceUnavailable);
+					return new WebResult().Invalidate(localizer["This browser did not subscribe: {0}", browser?.Error ?? "?"], (int)HttpStatusCode.BadRequest);
 				}
 
 				var result = await Tell(device, entry.PersonaId, browser, cancellationToken);