fix: prevent PricingHandler panics in offline mode

**Problem:**
Opening /admin/pricing page caused nil pointer panic when offline
because PricingHandler methods accessed nil repositories.

**Solution:**
Added offline checks to all PricingHandler public methods:

1. **GetStats** - returns empty stats with offline flag
2. **ListComponents** - returns empty list with message
3. **GetComponentPricing** - returns 503 with offline error
4. **UpdatePrice** - blocks mutations with offline error
5. **RecalculateAll** - blocks recalculation with offline error
6. **PreviewPrice** - blocks preview with offline error

**Response format:**
```json
{
  "offline": true,
  "message": "Управление ценами доступно только в онлайн режиме",
  "components": [],
  "total": 0
}
```

**Impact:**
- ✅ No panics when viewing admin pricing offline
- ✅ Clear offline status indication
- ✅ Graceful degradation for all operations
- ✅ UI can detect offline and show appropriate message

Fixes Phase 2.5 admin panel offline issue.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

internal/handlers/pricing.go

@@ -68,6 +68,17 @@ func NewPricingHandler(
 }
 
 func (h *PricingHandler) GetStats(c *gin.Context) {
+	// Check if we're in offline mode
+	if h.statsRepo == nil || h.alertService == nil {
+		c.JSON(http.StatusOK, gin.H{
+			"new_alerts_count":    0,
+			"top_components":      []interface{}{},
+			"trending_components": []interface{}{},
+			"offline":             true,
+		})
+		return
+	}
+
 	newAlerts, _ := h.alertService.GetNewAlertsCount()
 	topComponents, _ := h.statsRepo.GetTopComponents(10)
 	trendingComponents, _ := h.statsRepo.GetTrendingComponents(10)
@@ -86,6 +97,19 @@ type ComponentWithCount struct {
 }
 
 func (h *PricingHandler) ListComponents(c *gin.Context) {
+	// Check if we're in offline mode
+	if h.componentRepo == nil {
+		c.JSON(http.StatusOK, gin.H{
+			"components": []ComponentWithCount{},
+			"total":      0,
+			"page":       1,
+			"per_page":   20,
+			"offline":    true,
+			"message":    "Управление ценами доступно только в онлайн режиме",
+		})
+		return
+	}
+
 	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
 	perPage, _ := strconv.Atoi(c.DefaultQuery("per_page", "20"))
 
@@ -213,6 +237,15 @@ func (h *PricingHandler) expandMetaPrices(metaPrices, excludeLot string) []strin
 }
 
 func (h *PricingHandler) GetComponentPricing(c *gin.Context) {
+	// Check if we're in offline mode
+	if h.componentRepo == nil || h.pricingService == nil {
+		c.JSON(http.StatusServiceUnavailable, gin.H{
+			"error":   "Управление ценами доступно только в онлайн режиме",
+			"offline": true,
+		})
+		return
+	}
+
 	lotName := c.Param("lot_name")
 
 	component, err := h.componentRepo.GetByLotName(lotName)
@@ -248,6 +281,15 @@ type UpdatePriceRequest struct {
 }
 
 func (h *PricingHandler) UpdatePrice(c *gin.Context) {
+	// Check if we're in offline mode
+	if h.db == nil {
+		c.JSON(http.StatusServiceUnavailable, gin.H{
+			"error":   "Обновление цен доступно только в онлайн режиме",
+			"offline": true,
+		})
+		return
+	}
+
 	var req UpdatePriceRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
 		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
@@ -409,6 +451,15 @@ func (h *PricingHandler) recalculateSinglePrice(lotName string) {
 }
 
 func (h *PricingHandler) RecalculateAll(c *gin.Context) {
+	// Check if we're in offline mode
+	if h.db == nil {
+		c.JSON(http.StatusServiceUnavailable, gin.H{
+			"error":   "Пересчёт цен доступен только в онлайн режиме",
+			"offline": true,
+		})
+		return
+	}
+
 	// Set headers for SSE
 	c.Header("Content-Type", "text/event-stream")
 	c.Header("Cache-Control", "no-cache")
@@ -667,6 +718,15 @@ type PreviewPriceRequest struct {
 }
 
 func (h *PricingHandler) PreviewPrice(c *gin.Context) {
+	// Check if we're in offline mode
+	if h.db == nil {
+		c.JSON(http.StatusServiceUnavailable, gin.H{
+			"error":   "Предпросмотр цены доступен только в онлайн режиме",
+			"offline": true,
+		})
+		return
+	}
+
 	var req PreviewPriceRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
 		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})