fix: rename deepseek model from deepseek-chat to deepseek-v4-pro

DeepSeek API deprecated deepseek-chat model. Returns error:
'the supported API model names are deepseek-v4-pro or deepseek-v4-flash'

Affected all 4 AI endpoints:
- risk-flags (90-day dashboard)
- triage-suggest
- rca-draft
- quality-check

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

app/api/incidents/[id]/ai/triage-suggest/route.ts

@@ -50,7 +50,7 @@ export async function POST(
   let res: Awaited<ReturnType<typeof client.chat.completions.create>>
   try {
     res = await client.chat.completions.create({
-      model: 'deepseek-chat',
+      model: 'deepseek-v4-pro',
       max_tokens: 1024,
       tools: [{
         type: 'function',
@@ -118,7 +118,7 @@ Suggest severity (1–5) and tick the appropriate NADOPOD 2004 flags. Give a one
   }
 
   await withUser(session.sub, async tx => {
-    await writeAuditLog(tx, 'incidents', id, 'ai_triage_suggest', { suggestion: input, model: 'deepseek-chat' })
+    await writeAuditLog(tx, 'incidents', id, 'ai_triage_suggest', { suggestion: input, model: 'deepseek-v4-pro' })
   })
 
   return NextResponse.json(input)