feat: ticket watchers, fulltext search, single-query pagination, watcher notifications

Ticket watchers:
- api/watch_ticket.php: GET (watch state) + POST (watch/unwatch toggle)
- index.php: route for /api/watch_ticket.php
- TicketView: WATCH/UNWATCH button with live state fetch and toggle
- NotificationHelper::notifyWatchers(): fetches watchers from DB, resolves
  Matrix IDs via Synapse, fires notification to watchers + global list
- add_comment.php, update_ticket.php: call notifyWatchers on comment and
  status-change events respectively

Fulltext search:
- TicketModel::hasFulltextIndex(): detects FULLTEXT index via information_schema
- getAllTickets(): uses MATCH...AGAINST when fulltext index exists, LIKE fallback
  when not yet applied — zero-downtime rollout

Single-query pagination:
- getAllTickets() replaces separate COUNT + SELECT with COUNT(*) OVER() window
  function — one round trip to DB per page load instead of two

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

views/TicketView.php

@@ -132,6 +132,8 @@ include __DIR__ . '/layout_header.php';
         </option>
       <?php endforeach ?>
     </select>
+    <button type="button" id="watchButton" class="lt-btn lt-btn-ghost lt-btn-sm"
+            title="Watch this ticket to receive Matrix notifications on updates">WATCH</button>
     <button type="button" id="editButton" class="lt-btn lt-btn-primary lt-btn-sm">EDIT</button>
     <button type="button" id="cloneButton" class="lt-btn lt-btn-sm">CLONE</button>
     <a id="exportFullBtn"
@@ -768,6 +770,49 @@ document.addEventListener('DOMContentLoaded', function () {
         });
     }
 
+    // Watch / Unwatch button
+    var watchBtn = document.getElementById('watchButton');
+    if (watchBtn) {
+        var _watching = false;
+        // Fetch initial state
+        lt.api.get('/api/watch_ticket.php?ticket_id=' + window.ticketData.ticket_id)
+            .then(function (d) {
+                if (d.success) {
+                    _watching = d.watching;
+                    watchBtn.textContent = _watching ? 'UNWATCH' : 'WATCH';
+                    watchBtn.title = _watching
+                        ? 'You are watching this ticket. Click to stop.'
+                        : 'Watch this ticket for Matrix notifications on updates.';
+                    if (_watching) watchBtn.classList.add('lt-btn-active');
+                }
+            })
+            .catch(function () {});
+
+        watchBtn.addEventListener('click', function () {
+            var action = _watching ? 'unwatch' : 'watch';
+            watchBtn.disabled = true;
+            lt.api.post('/api/watch_ticket.php', { ticket_id: window.ticketData.ticket_id, action: action })
+                .then(function (d) {
+                    if (d.success) {
+                        _watching = d.watching;
+                        watchBtn.textContent = _watching ? 'UNWATCH' : 'WATCH';
+                        watchBtn.title = _watching
+                            ? 'You are watching this ticket. Click to stop.'
+                            : 'Watch this ticket for Matrix notifications on updates.';
+                        watchBtn.classList.toggle('lt-btn-active', _watching);
+                        lt.toast.success(_watching ? 'Watching ticket' : 'Stopped watching ticket');
+                    } else {
+                        lt.toast.error('Failed: ' + (d.error || 'Unknown error'));
+                    }
+                    watchBtn.disabled = false;
+                })
+                .catch(function () {
+                    lt.toast.error('Failed to update watch status');
+                    watchBtn.disabled = false;
+                });
+        });
+    }
+
     // Add comment button
     var addCommentBtn = document.getElementById('addCommentBtn');
     if (addCommentBtn) {