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

Components/Daisy/DataDisplay/DHoverGallery.razor

@@ -4,19 +4,16 @@
    across it shows the others. Up to 10 images of the same size, from Images or as <img> children; cap its width in
    Class (max-w-60), or it fills the container. *@
 <figure @attributes="AdditionalAttributes" class="@Cx("hover-gallery", Class)">
-	@if (Images is not null)
+	@foreach (var src in Images.Take(10))
 	{
-		foreach (var src in Images.Take(10))
-		{
-			<img src="@src" alt="@Alt" />
-		}
+		<img src="@src" alt="@(Alt ?? "")" />
 	}
 	@ChildContent
 </figure>
 
 @code {
-	[Parameter] public IEnumerable<string> Images { get; set; }
+	[Parameter] public IEnumerable<string> Images { get; set; } = [];
 	// "" on purpose (the documented exception to "no string defaults"): an empty alt marks a decorative image.
-	[Parameter] public string Alt { get; set; } = "";
+	[Parameter] public string Alt { get; set; }
 	[Parameter] public RenderFragment ChildContent { get; set; }
 }