Fix crypto.randomUUID not available in all environments

Replace with a simple counter-based temp ID generator for optimistic
UI messages.

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

frontend/src/views/chat/ChatView.vue

@@ -133,6 +133,11 @@ import { chatApi } from '@/services/chat'
 import ChatToolResult from './ChatToolResult.vue'
 import type { ChatConversation, ChatMessage } from '@/types'
 
+let _idCounter = 0
+function tempId(): string {
+  return `temp-${Date.now()}-${++_idCounter}`
+}
+
 const conversations = ref<ChatConversation[]>([])
 const messages = ref<ChatMessage[]>([])
 const activeConversationId = ref<string | null>(null)
@@ -189,7 +194,7 @@ async function sendMessage() {
 
   // Add user message optimistically
   const userMsg: ChatMessage = {
-    id: crypto.randomUUID(),
+    id: tempId(),
     role: 'user',
     content: text,
     toolResultType: null,
@@ -218,7 +223,7 @@ async function sendMessage() {
     messages.value.push(data.assistantMessage)
   } catch (err: any) {
     messages.value.push({
-      id: crypto.randomUUID(),
+      id: tempId(),
       role: 'assistant',
       content: err.response?.data?.message || 'Sorry, something went wrong. Please check that Ollama is running and try again.',
       toolResultType: null,