feat: test version of unit swap tool.

templates/tools.html

@@ -141,6 +141,24 @@
         </div>
     </a>
 
+    <!-- Unit Swap -->
+    <a href="/tools/unit-swap"
+       class="block bg-white dark:bg-slate-800 rounded-xl shadow-lg p-5 hover:shadow-xl transition-shadow border border-transparent hover:border-seismo-orange">
+        <div class="flex items-start gap-3">
+            <div class="w-10 h-10 rounded-lg bg-amber-100 dark:bg-amber-900/30 text-amber-600 dark:text-amber-400 flex items-center justify-center shrink-0">
+                <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M7 16V4m0 0L3 8m4-4l4 4m6 0v12m0 0l4-4m-4 4l-4-4"/>
+                </svg>
+            </div>
+            <div class="flex-1 min-w-0">
+                <h3 class="font-semibold text-gray-900 dark:text-white">Unit Swap</h3>
+                <p class="text-sm text-gray-600 dark:text-gray-400 mt-1">
+                    Field-swap a unit (and modem) at a vibration location. Pick project → location → incoming unit → confirm. Optional photo of the new install.
+                </p>
+            </div>
+        </div>
+    </a>
+
     <!-- Swap Detection (Phase 5c — coming soon) -->
     <div class="bg-gray-50 dark:bg-slate-800/50 rounded-xl shadow p-5 border border-dashed border-gray-300 dark:border-gray-700 cursor-not-allowed">
         <div class="flex items-start gap-3">