Replace crypto.randomUUID with fallback for HTTP contexts

crypto.randomUUID() requires secure context (HTTPS).
Use Date.now + Math.random fallback for session ID generation.

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

app/static/js/chat.js

@@ -3,7 +3,7 @@
 
 let chatSessionId = sessionStorage.getItem('chat_session');
 if (!chatSessionId) {
-    chatSessionId = crypto.randomUUID();
+    chatSessionId = 'sess-' + Date.now().toString(36) + '-' + Math.random().toString(36).slice(2, 10);
     sessionStorage.setItem('chat_session', chatSessionId);
 }