feat: refine the reviewer explorer and the visual system

- Explorer: redacted terms are highlighted in Markdown and code, the
  sidebar shows when the link expires, "Download repository" is the one
  primary action, and signed-out reviewers get a header without Sign in
  or the source-code link.
- Status: a ready anonymization leads with a copyable share link; the
  support links sit flat inside their section.
- One primary colour (accent) for actions and progress; mono is kept for
  IDs, hashes and paths; settings are plain sections instead of cards.
- Font sizes snap to one scale (10-40px); rem values keep following the
  reader's browser font size.
- Ko-fi button uses a dark surface in dark mode instead of a white pill.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

public/script/main.js

@@ -7,7 +7,7 @@ import { render as iconsTemplate } from "../partials/icons.htm";
 import { initializeTemplate } from "./template-state.js";
 import { createPageState, createTimers } from "./state.js";
 import { createHttp, promises } from "./http.js";
-import { mainController } from "./app.js";
+import { mainController, highlightRedactions } from "./app.js";
 import { createQuotaService } from "./quota.js";
 import * as formatters from "./formatters.js";
 import translations from "../i18n/locale-en.json";
@@ -82,6 +82,7 @@ export function mountApplication(target = "#app", options = {}) {
       root.window = window;
       root.Math = Math;
       root.sanitize = value => DOMPurify.sanitize(value ?? "");
+      root.highlightRedactions = html => highlightRedactions(html, root.site_options?.ANONYMIZATION_MASK);
       root.submitForm = submitForm;
       root.safeUrl = safeUrl;
       const context = services();