Add screenshot uploads to feedback modal, Webex bot DM on issue close

- Feedback modal now supports up to 3 image attachments (PNG/JPG/GIF/WebP, 5MB
  each) with thumbnail previews. Images are uploaded to GitLab project uploads
  and embedded as markdown in the issue description.
- New webhook endpoint (POST /api/webhooks/gitlab) receives issue close events,
  parses the submitter from the description, looks up their email, and sends a
  Webex DM via the Patches O'Houlihan bot.
- New helper: backend/helpers/webexBot.js (fire-and-forget DM sender).
- Requires WEBEX_BOT_TOKEN and GITLAB_WEBHOOK_SECRET in backend/.env.

backend/helpers/webexBot.js

@@ -0,0 +1,64 @@
+// Webex Bot DM Helper
+// Fire-and-forget pattern — logs success/failure but never throws.
+// Used to notify users when their feedback issues are resolved.
+
+const https = require('https');
+
+const WEBEX_API_URL = 'https://webexapis.com/v1/messages';
+const WEBEX_BOT_TOKEN = process.env.WEBEX_BOT_TOKEN || '';
+
+/**
+ * Send a direct message to a user via Webex Teams bot.
+ * @param {string} email - Recipient's email address
+ * @param {string} markdownMessage - Message body (Webex markdown supported)
+ */
+function sendDirectMessage(email, markdownMessage) {
+    if (!WEBEX_BOT_TOKEN) {
+        console.warn('[WebexBot] WEBEX_BOT_TOKEN not configured — skipping DM');
+        return;
+    }
+
+    if (!email || !markdownMessage) {
+        console.warn('[WebexBot] Missing email or message — skipping DM');
+        return;
+    }
+
+    const postData = JSON.stringify({
+        toPersonEmail: email,
+        markdown: markdownMessage,
+    });
+
+    const parsed = new URL(WEBEX_API_URL);
+
+    const reqOpts = {
+        method: 'POST',
+        hostname: parsed.hostname,
+        path: parsed.pathname,
+        headers: {
+            'Content-Type': 'application/json',
+            'Authorization': `Bearer ${WEBEX_BOT_TOKEN}`,
+            'Content-Length': Buffer.byteLength(postData),
+        },
+    };
+
+    const req = https.request(reqOpts, (res) => {
+        let data = '';
+        res.on('data', chunk => { data += chunk; });
+        res.on('end', () => {
+            if (res.statusCode >= 200 && res.statusCode < 300) {
+                console.log(`[WebexBot] DM sent to ${email} (${res.statusCode})`);
+            } else {
+                console.error(`[WebexBot] Failed to DM ${email} — ${res.statusCode}: ${data}`);
+            }
+        });
+    });
+
+    req.on('error', (err) => {
+        console.error(`[WebexBot] Request error sending DM to ${email}:`, err.message);
+    });
+
+    req.write(postData);
+    req.end();
+}
+
+module.exports = { sendDirectMessage };