feat(site): drop live demo, add Railway-style canvas preview

Remove all links to the deleted containr-app deployment and replace
the static hero screenshot with a CSS/HTML product mockup: a project
canvas with five icon-branded service nodes, connected edges (one
animated deploying edge), env/zoom/minimap pills, status dots,
domains, and image tags. Mobile gets a two-column layout with its
own edge paths.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

site/templates.html

@@ -317,7 +317,7 @@
       <a class="gh-link" href="https://github.com/Dvorinka/Containr" target="_blank" rel="noopener" aria-label="Containr on GitHub">
         <svg width="16" height="16" viewBox="0 0 16 16" fill="currentColor"><path d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27s1.36.09 2 .27c1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.01 8.01 0 0 0 16 8c0-4.42-3.58-8-8-8Z"/></svg>
       </a>
-      <a class="btn btn-primary" href="https://containr-app.vercel.app/projects">Live demo</a>
+      <a class="btn btn-primary" href="index.html#install">Get started</a>
     </div>
   </div>
 </nav>
@@ -370,7 +370,6 @@
         <svg width="13" height="13" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><rect x="9" y="9" width="12" height="12" rx="2"/><path d="M5 15H4a2 2 0 0 1-2-2V4a2 2 0 0 1 2-2h9a2 2 0 0 1 2 2v1"/></svg>
         Copy template JSON
       </button>
-      <a class="btn btn-ghost" id="m-open" href="https://containr-app.vercel.app/templates" target="_blank" rel="noopener">Open in demo app</a>
       <a class="btn btn-ghost" href="https://github.com/Dvorinka/Containr/tree/main/docs/guides" target="_blank" rel="noopener">Deploy guide</a>
     </div>
     <p class="hint">In your instance: <code>Templates &rarr; New template &rarr; Upload .json</code> (or paste the copied JSON). Deploy it to any project from there.</p>
@@ -381,7 +380,6 @@
   <div class="wrap foot">
     <span class="l"><img src="containr.svg" alt="">Containr - MIT License</span>
     <nav>
-      <a href="https://containr-app.vercel.app/projects">Live demo</a>
       <a href="https://github.com/Dvorinka/Containr" target="_blank" rel="noopener">GitHub</a>
       <a href="https://github.com/Dvorinka/Containr/tree/main/docs" target="_blank" rel="noopener">Docs</a>
       <a href="https://github.com/Dvorinka/Containr/blob/main/CONTRIBUTING.md" target="_blank" rel="noopener">Contribute</a>
@@ -395,7 +393,6 @@
   // Point it at an instance once with ?api=https://host (persisted in
   // localStorage); with no instance configured the bundled official
   // snapshot renders immediately.
-  const APP_BASE = 'https://containr-app.vercel.app';
   const params = new URLSearchParams(location.search);
   const paramApi = params.get('api');
   if (paramApi) localStorage.setItem('containr-api', paramApi.replace(/\/$/, ''));
@@ -541,7 +538,6 @@
     document.getElementById('m-badges').innerHTML =
       badge(t) + `<span class="badge" style="background:var(--surface-muted);color:var(--text-tertiary)">${esc(t.category || 'custom')}</span>`;
     document.getElementById('m-desc').textContent = t.description || 'No description.';
-    document.getElementById('m-open').href = `${APP_BASE}/templates?template=${encodeURIComponent(t.id)}`;
 
     const c = cfg(t);
     const meta = [];