fix: Handle null values in dashboard API to prevent React error #306

Fixed critical React error #306 by adding proper null handling for
reasoning and consequence fields in the dashboard service.

Issue: When database columns (reasoning, consequence) contain NULL
values, Python's .get() method returns None, which becomes undefined
in JavaScript, causing React to throw error #306 when trying to render.

Solution: Changed from `.get("field", "default")` to `.get("field") or "default"`
to properly handle None values throughout the dashboard service.

Changes:
- Purchase order actions: Added null coalescing for reasoning/consequence
- Production timeline: Added null coalescing for reasoning field
- Alert actions: Added null coalescing for description and source
- Onboarding actions: Added null coalescing for title and consequence

This ensures all text fields always have valid string values before
being sent to the frontend, preventing undefined rendering errors.

services/orchestrator/app/services/dashboard_service.py

@@ -352,8 +352,8 @@ class DashboardService:
                     "type": ActionType.RESOLVE_ALERT,
                     "urgency": ActionUrgency.CRITICAL,
                     "title": alert["title"],
-                    "subtitle": alert.get("source", "System Alert"),
+                    "subtitle": alert.get("source") or "System Alert",
-                    "reasoning": alert.get("description", ""),
+                    "reasoning": alert.get("description") or "System alert requires attention",
                     "consequence": "Immediate action required to prevent production issues",
                     "actions": [
                         {"label": "View Details", "type": "primary", "action": "view_alert"},
@@ -373,8 +373,8 @@ class DashboardService:
                 "urgency": urgency,
                 "title": f"Purchase Order {po.get('po_number', 'N/A')}",
                 "subtitle": f"Supplier: {po.get('supplier_name', 'Unknown')}",
-                "reasoning": po.get("reasoning", "Low stock levels detected"),
+                "reasoning": po.get("reasoning") or "Low stock levels detected",
-                "consequence": po.get("consequence", "Order needed to maintain inventory levels"),
+                "consequence": po.get("consequence") or "Order needed to maintain inventory levels",
                 "amount": po.get("total_amount", 0),
                 "currency": po.get("currency", "EUR"),
                 "actions": [
@@ -393,14 +393,14 @@ class DashboardService:
                         "id": f"onboarding_{step['id']}",
                         "type": ActionType.COMPLETE_ONBOARDING,
                         "urgency": ActionUrgency.IMPORTANT,
-                        "title": step["title"],
+                        "title": step.get("title") or "Complete onboarding step",
                         "subtitle": "Setup incomplete",
                         "reasoning": "Required to unlock full automation",
-                        "consequence": step.get("consequence", "Some features are limited"),
+                        "consequence": step.get("consequence") or "Some features are limited",
                         "actions": [
                             {"label": "Complete Setup", "type": "primary", "action": "complete_onboarding"}
                         ],
-                        "estimatedTimeMinutes": step.get("estimated_minutes", 10)
+                        "estimatedTimeMinutes": step.get("estimated_minutes") or 10
                     })
 
         # Sort by urgency priority
@@ -505,7 +505,7 @@ class DashboardService:
                 "progress": progress,
                 "readyBy": planned_end.isoformat() if planned_end else None,
                 "priority": batch.get("priority", "MEDIUM"),
-                "reasoning": batch.get("reasoning", "Based on demand forecast")
+                "reasoning": batch.get("reasoning") or "Based on demand forecast"
             })
 
         # Sort by planned start time