Replace Discord webhook notifications with Matrix (hookshot)

- Add helpers/NotificationHelper.php: shared Matrix webhook sender
  that reads MATRIX_WEBHOOK_URL and MATRIX_NOTIFY_USERS from config
- Remove sendDiscordWebhook() from TicketController; call
  NotificationHelper::sendTicketNotification() instead
- Replace 60-line Discord embed block in create_ticket_api.php
  with a single NotificationHelper call
- config/config.php: DISCORD_WEBHOOK_URL → MATRIX_WEBHOOK_URL +
  new MATRIX_NOTIFY_USERS key (comma-separated Matrix user IDs)
- .env.example: updated env var names and comments

Payload sent to hookshot includes notify_users array so the
JS transform can build proper @mention links for each user.

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

create_ticket_api.php

@@ -227,66 +227,12 @@ if ($stmt->execute()) {
 $stmt->close();
 $conn->close();
 
-// Discord webhook notification
-if (isset($envVars['DISCORD_WEBHOOK_URL']) && !empty($envVars['DISCORD_WEBHOOK_URL'])) {
-    $discord_webhook_url = $envVars['DISCORD_WEBHOOK_URL'];
-
-    // Map priorities to Discord colors (decimal format)
-    $priorityColors = [
-        "1" => 0xDC3545, // P1 Critical - Red
-        "2" => 0xFD7E14, // P2 High - Orange
-        "3" => 0x0DCAF0, // P3 Medium - Cyan
-        "4" => 0x198754, // P4 Low - Green
-        "5" => 0x6C757D  // P5 Info - Gray
-    ];
-
-    // Priority labels for display
-    $priorityLabels = [
-        "1" => "P1 - Critical",
-        "2" => "P2 - High",
-        "3" => "P3 - Medium",
-        "4" => "P4 - Low",
-        "5" => "P5 - Info"
-    ];
-
-    // Create ticket URL using validated host
-    $ticketUrl = UrlHelper::ticketUrl($ticket_id);
-
-    // Extract hostname from title for cleaner display
-    preg_match('/^\[([^\]]+)\]/', $title, $hostnameMatch);
-    $sourceHost = $hostnameMatch[1] ?? 'Unknown';
-
-    $discord_data = [
-        "embeds" => [[
-            "title" => "New Ticket Created",
-            "description" => "**#{$ticket_id}** - {$title}",
-            "url" => $ticketUrl,
-            "color" => $priorityColors[$priority] ?? 0x6C757D,
-            "fields" => [
-                ["name" => "Priority", "value" => $priorityLabels[$priority] ?? "P{$priority}", "inline" => true],
-                ["name" => "Category", "value" => $category, "inline" => true],
-                ["name" => "Type", "value" => $type, "inline" => true],
-                ["name" => "Status", "value" => $status, "inline" => true],
-                ["name" => "Source", "value" => $sourceHost, "inline" => true]
-            ],
-            "footer" => [
-                "text" => "Tinker Tickets | Automated Alert"
-            ],
-            "timestamp" => date('c')
-        ]]
-    ];
-
-    $ch = curl_init($discord_webhook_url);
-    curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
-    curl_setopt($ch, CURLOPT_POST, 1);
-    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($discord_data));
-    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
-    curl_setopt($ch, CURLOPT_TIMEOUT, 10);
-    $webhookResult = curl_exec($ch);
-    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
-    curl_close($ch);
-
-    if ($httpCode !== 204 && $httpCode !== 200) {
-        error_log("Discord webhook failed for ticket #{$ticket_id}. HTTP Code: {$httpCode}");
-    }
-}
+// Matrix webhook notification
+require_once __DIR__ . '/helpers/NotificationHelper.php';
+NotificationHelper::sendTicketNotification($ticket_id, [
+    'title'    => $title,
+    'priority' => $priority,
+    'category' => $category,
+    'type'     => $type,
+    'status'   => $status,
+], 'automated');