feat: Add i18n support for AI insights with structured reasoning

Complete i18n implementation for internal service reasoning:
- Update AIInsight interface to include reasoning_data field
- Integrate useReasoningTranslation hook in AI Insights page
- Add translation keys for safety stock, price forecaster, and optimization

Translation coverage (EN/ES/EU):
- Safety Stock: statistical z-score, advanced variability, fixed percentage, errors
- Price Forecaster: price change predictions, volatility alerts, buying recommendations
- Optimization: EOQ calculations, MOQ/max constraints, tier pricing

Benefits:
- AI insights now display in user's preferred language
- Consistent with PO/Batch reasoning translation pattern
- Structured parameters enable rich, contextualized translations
- Falls back gracefully to description field if translation missing

Implementation:
- frontend/src/api/services/aiInsights.ts: Add reasoning_data to interface
- frontend/src/pages/app/analytics/ai-insights/AIInsightsPage.tsx: Translate insights
- frontend/src/locales/*/reasoning.json: Add safetyStock, priceForecaster, optimization keys

This completes the full i18n implementation for the bakery AI system.

frontend/src/locales/en/reasoning.json

@@ -44,6 +44,29 @@
     "LEAD_TIME_INVALID": "Lead time or demand deviation is zero or negative",
     "NO_DEMAND_DATA": "No historical demand data available (minimum 2 data points required)"
   },
+  "safetyStock": {
+    "statistical_z_score": "Safety stock calculated using statistical method (service level {{service_level}}%, z-score {{z_score}}). Based on demand std dev {{demand_std_dev}} and {{lead_time_days}}-day lead time. Result: {{safety_stock}} units.",
+    "advanced_variability": "Safety stock calculated with advanced variability analysis. Accounts for both demand variability (σ={{demand_std_dev}}) and lead time uncertainty (σ={{lead_time_std_dev}} days). Result: {{safety_stock}} units.",
+    "fixed_percentage": "Safety stock set at {{percentage}}% of {{lead_time_days}}-day demand ({{lead_time_demand}} units). Result: {{safety_stock}} units.",
+    "error_lead_time_invalid": "Cannot calculate safety stock: lead time ({{lead_time_days}} days) or demand std dev ({{demand_std_dev}}) is invalid.",
+    "error_insufficient_data": "Insufficient demand history for safety stock calculation ({{data_points}} data points, need {{min_required}})."
+  },
+  "priceForecaster": {
+    "decrease_expected": "Price expected to decrease {{change_pct}}% over next {{forecast_days}} days. Current: €{{current_price}}, forecast: €{{forecast_mean}}. Recommendation: Wait for better price.",
+    "increase_expected": "Price expected to increase {{change_pct}}% over next {{forecast_days}} days. Current: €{{current_price}}, forecast: €{{forecast_mean}}. Recommendation: Buy now to lock in current price.",
+    "high_volatility": "High price volatility detected (CV={{coefficient}}). Average daily price change: {{avg_daily_change_pct}}%. Recommendation: Wait for price dip.",
+    "below_average": "Current price €{{current_price}} is {{below_avg_pct}}% below historical average (€{{mean_price}}). Favorable buying opportunity.",
+    "stable": "Price is stable. Current: €{{current_price}}, forecast: €{{forecast_mean}} ({{expected_change_pct}}% change expected). Normal procurement timing recommended.",
+    "insufficient_data": "Insufficient price history for reliable forecast ({{history_days}} days available, need {{min_required_days}} days)."
+  },
+  "optimization": {
+    "eoq_base": "Economic Order Quantity calculated: {{eoq}} units (required: {{required_quantity}}, annual demand: {{annual_demand}}). Optimized for {{optimal_quantity}} units.",
+    "moq_applied": "Minimum order quantity constraint applied: {{moq}} units.",
+    "max_applied": "Maximum order quantity constraint applied: {{max_qty}} units.",
+    "no_tiers": "No price tiers available for this product. Base quantity: {{base_quantity}} units at €{{unit_price}} per unit.",
+    "current_tier": "Current pricing tier: €{{current_tier_price}} per unit for {{base_quantity}} units (total: €{{base_cost}}).",
+    "tier_upgraded": "Upgraded to better price tier! Ordering {{tier_min_qty}} units ({{additional_qty}} extra) at €{{tier_price}} per unit saves €{{savings}} compared to {{base_quantity}} units at €{{base_price}}."
+  },
   "jtbd": {
     "health_status": {
       "green": "Everything is running smoothly",