feat(ui): auth-gate the landing, add Help page and Home nav

- Landing shows the tool tiles only when signed in and a sign-in card
  otherwise; the login callback now returns to /.
- New public /help page: intro plus a per-tool Carbon accordion.
- Nav restructured to Home, {services}, divider, Help, Sign In/Out in
  both the header and the side nav; the header right keeps only the
  identity chip. Side-nav logo enlarged, border removed, spacing
  equalised. Sign-out modal no longer flashes before it is defined.
- Per-deploy asset versioning (?v=) with immutable asset caching and
  no-store HTML; help step lists show their numbers again.
- Tests updated and extended (48 total).

tools/public/index.html

@@ -22,36 +22,10 @@
   <main class="container">
     <div class="hero">
       <h1>YOUreka Tools</h1>
-      <p>Field utilities for YOUreka ID Domains. Sign in with your YOUreka account to use the tools that require it.</p>
+      <p>Field utilities for YOUreka ID Domains.</p>
     </div>
 
-    <div class="tool-grid">
-      <cds-clickable-tile href="/cropper">
-        <div class="tool-card">
-          <span class="tool-icon">
-            <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M6 2v14a2 2 0 0 0 2 2h14"/><path d="M18 22V8a2 2 0 0 0-2-2H2"/></svg>
-          </span>
-          <h3>Image Cropper</h3>
-          <p>Review, crop and save identity photos submitted for YOUreka ID domain profiles.</p>
-          <span class="go">Open Image Cropper
-            <svg viewBox="0 0 24 24" width="14" height="14" fill="none" stroke="currentColor" stroke-width="2.2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M5 12h14"/><path d="m12 5 7 7-7 7"/></svg>
-          </span>
-        </div>
-      </cds-clickable-tile>
-
-      <cds-clickable-tile href="/fingerprint">
-        <div class="tool-card">
-          <span class="tool-icon">
-            <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M12 2a8 8 0 0 0-8 8c0 3.5 1 5.5 2 7"/><path d="M16 21a10 10 0 0 0 4-13 8 8 0 0 0-15.7-1"/><path d="M8 21a8 8 0 0 1-1-11 5 5 0 0 1 9.7 1.4A6 6 0 0 1 12 17"/><path d="M12 21a4 4 0 0 0 4-4 4 4 0 0 0-1.2-2.9"/></svg>
-          </span>
-          <h3>Fingerprint Agent</h3>
-          <p>Enroll staff fingerprints with the scanner attached to this laptop. Captures are authorized per domain.</p>
-          <span class="go">Open Fingerprint Agent
-            <svg viewBox="0 0 24 24" width="14" height="14" fill="none" stroke="currentColor" stroke-width="2.2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M5 12h14"/><path d="m12 5 7 7-7 7"/></svg>
-          </span>
-        </div>
-      </cds-clickable-tile>
-    </div>
+    <!--landing-view-->
   </main>
 
   <footer class="foot">