Make the home page's AS name search work (closes #151)

The AS Name Search card on the home page said the search was coming soon.
It now asks the new GET /api/v1/search/as?q=<text> and lists the matches
as links to their AS pages. asinfo.Search ignores case, returns the first
matches up to a limit in AS number order, and counts all matches. An
empty q answers 400.

When the database has no record of an AS, its page and /api/v1/as/{asn}
take its handle and description from asinfo and still list its prefixes.
They answer 404 only for an AS with no record, no asinfo entry and no
prefix. AS 0 means no known origin: it always answers 404, and the search
never lists it.

Model: opus-5-5

internal/templates/index.html

@@ -174,6 +174,38 @@
         #asname-results .search-message {
             font-size: 13px;
         }
+        #asname-results .error {
+            color: #c00;
+        }
+        .asname-list {
+            list-style: none;
+            margin: 12px 0 0 0;
+            padding: 0;
+            max-height: 400px;
+            overflow-y: auto;
+        }
+        .asname-list li {
+            border-bottom: 1px solid #eee;
+        }
+        .asname-list a {
+            display: block;
+            padding: 8px 4px;
+            color: #2c3e50;
+            text-decoration: none;
+            font-size: 14px;
+        }
+        .asname-list a:hover {
+            background: #f5f5f5;
+        }
+        .asname-list .asn {
+            font-weight: 600;
+            color: #3498db;
+        }
+        .asname-list .description {
+            display: block;
+            color: #7f8c8d;
+            font-size: 12px;
+        }
 
         /* IP Lookup result */
         .ip-result {
@@ -306,7 +338,7 @@
                     <input type="text" id="asname-input" placeholder="e.g., Google, Cloudflare" autocomplete="off">
                     <button type="submit">Search</button>
                 </form>
-                <p class="search-hint">Search for autonomous systems by organization name</p>
+                <p class="search-hint">Search for autonomous systems by organization name or handle</p>
                 <div id="asname-results"></div>
             </div>
 
@@ -387,24 +419,82 @@
             }
         });
 
-        // AS name search
+        // AS name search. The handles and descriptions come from outside data,
+        // so the results are built with textContent, never innerHTML.
+        const asNameResults = document.getElementById('asname-results');
+
+        // Replace the search results with one line of text.
+        function showASNameMessage(text, className) {
+            const line = document.createElement('p');
+            line.className = className;
+            line.textContent = text;
+            asNameResults.replaceChildren(line);
+        }
+
+        // List the matches of a search answer, each as a link to its AS page,
+        // and say how many more matched than the answer holds.
+        function showASNameMatches(data) {
+            if (data.total === 0) {
+                showASNameMessage('No AS matches "' + data.query + '".', 'search-message');
+                return;
+            }
+
+            const list = document.createElement('ul');
+            list.className = 'asname-list';
+            for (const match of data.results) {
+                const asn = document.createElement('span');
+                asn.className = 'asn';
+                asn.textContent = 'AS' + match.asn;
+
+                const description = document.createElement('span');
+                description.className = 'description';
+                description.textContent = match.description;
+
+                const link = document.createElement('a');
+                link.href = '/as/' + match.asn;
+                link.append(asn, ' ' + match.handle, description);
+
+                const item = document.createElement('li');
+                item.append(link);
+                list.append(item);
+            }
+            asNameResults.replaceChildren(list);
+
+            const more = data.total - data.results.length;
+            if (more > 0) {
+                const line = document.createElement('p');
+                line.className = 'search-message';
+                line.textContent = more.toLocaleString() + ' more matched. Narrow the search to see them.';
+                asNameResults.append(line);
+            }
+        }
+
         document.getElementById('asname-form').addEventListener('submit', function(e) {
             e.preventDefault();
             const query = document.getElementById('asname-input').value.trim();
             if (!query) return;
 
-            const resultsDiv = document.getElementById('asname-results');
-            resultsDiv.innerHTML = '<p class="loading">Searching...</p>';
-
-            // Use a simple client-side search against the asinfo data
-            // For now, redirect to AS page if it looks like an ASN
-            if (/^\d+$/.test(query)) {
-                window.location.href = '/as/' + query;
+            // A number, or AS and a number, opens that AS's page
+            const asn = query.replace(/^AS/i, '');
+            if (/^\d+$/.test(asn)) {
+                window.location.href = '/as/' + asn;
                 return;
             }
 
-            // Show a message that server-side search is coming
-            resultsDiv.innerHTML = '<p class="search-message">AS name search coming soon. For now, try an AS number.</p>';
+            showASNameMessage('Searching...', 'loading');
+
+            fetch('/api/v1/search/as?q=' + encodeURIComponent(query))
+                .then(response => response.json())
+                .then(response => {
+                    if (response.status === 'error') {
+                        showASNameMessage('Error: ' + response.error.msg, 'error');
+                    } else {
+                        showASNameMatches(response.data);
+                    }
+                })
+                .catch(error => {
+                    showASNameMessage('Error: ' + error.message, 'error');
+                });
         });
 
         // IP lookup