Add IP address search feature with global search box

- Add API endpoint GET /api/scans/by-ip/{ip_address} to retrieve
  last 10 scans containing a specific IP
- Add ScanService.get_scans_by_ip() method with ScanIP join query
- Add search box to global navigation header
- Create dedicated search results page at /search/ip
- Update API documentation with new endpoint

app/web/templates/base.html

@@ -76,6 +76,13 @@
                         </ul>
                     </li>
                 </ul>
+                <form class="d-flex me-3" action="{{ url_for('main.search_ip') }}" method="GET">
+                    <input class="form-control form-control-sm me-2" type="search" name="ip"
+                           placeholder="Search IP..." aria-label="Search IP" style="width: 150px;">
+                    <button class="btn btn-outline-primary btn-sm" type="submit">
+                        <i class="bi bi-search"></i>
+                    </button>
+                </form>
                 <ul class="navbar-nav">
                     <li class="nav-item">
                         <a class="nav-link {% if request.endpoint == 'main.help' %}active{% endif %}"