fix: load SignalIdModal on dashboard pages; clear status on zero matches

- Added signal-id-modal.js script to base_dashboard.html (nav button was silent on dashboard pages)
- Added else branch to clear "Searching…" status when zero matches returned

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/js/components/signal-id-modal.js

@@ -277,6 +277,8 @@ window.SignalIdModal = (function () {
             if (matches.length) {
                 _setStatus(matches.length + ' match' + (matches.length !== 1 ? 'es' : '')
                     + ' for ' + freq.toFixed(4) + ' MHz');
+            } else {
+                _setStatus('');
             }
             _renderResults(matches, freq);
         })

templates/layout/base_dashboard.html

@@ -184,6 +184,7 @@
 
 {% block scripts %}
 {{ super() }}
+<script src="{{ url_for('static', filename='js/components/signal-id-modal.js') }}{% if version %}?v={{ version }}{% endif %}"></script>
 <script>
     // Dashboard-specific scripts
     (function() {