feat: async AI calls, 10-min timeout, and failure messaging

- Make all AI endpoints (health scores + investment recommendations)
  fire-and-forget: POST returns immediately, frontend polls for results
- Extend AI API timeout from 2-5 min to 10 min for both services
- Add "last analysis failed — showing cached data" message to the
  Investment Recommendations panel (matches health score widgets)
- Add status/error_message columns to ai_recommendations table
- Remove nginx AI timeout overrides (no longer needed)
- Users can now navigate away during AI processing without interruption

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

backend/src/modules/investment-planning/investment-planning.controller.ts

@@ -36,9 +36,9 @@ export class InvestmentPlanningController {
   }
 
   @Post('recommendations')
-  @ApiOperation({ summary: 'Get AI-powered investment recommendations' })
+  @ApiOperation({ summary: 'Trigger AI-powered investment recommendations (async — returns immediately)' })
   @AllowViewer()
-  getRecommendations(@Req() req: any) {
-    return this.service.getAIRecommendations(req.user?.sub, req.user?.orgId);
+  triggerRecommendations(@Req() req: any) {
+    return this.service.triggerAIRecommendations(req.user?.sub, req.user?.orgId);
   }
 }