fix: improve provider and model data accuracy in dashboard

Updated handleGetProviders to include available models and last-used timestamps. Refined Model Pricing table to strictly filter by core providers and actual usage.

internal/server/dashboard.go

@@ -859,6 +859,28 @@ func (s *Server) handleGetProviders(c *gin.Context) {
 			}
 		}
 
+		// Get last used for this provider
+		var lastUsedTime sql.NullTime
+		_ = s.database.Get(&lastUsedTime, "SELECT MAX(timestamp) FROM llm_requests WHERE provider = ?", id)
+		var lastUsed interface{}
+		if lastUsedTime.Valid && !lastUsedTime.Time.IsZero() {
+			lastUsed = lastUsedTime.Time
+		}
+
+		// Get models for this provider from registry
+		var models []string
+		if s.registry != nil {
+			registryID := id
+			if id == "gemini" { registryID = "google" }
+			if id == "grok" { registryID = "xai" }
+			
+			if pInfo, ok := s.registry.Providers[registryID]; ok {
+				for mID := range pInfo.Models {
+					models = append(models, mID)
+				}
+			}
+		}
+
 		result = append(result, gin.H{
 			"id":                   id,
 			"name":                 name,
@@ -868,6 +890,8 @@ func (s *Server) handleGetProviders(c *gin.Context) {
 			"credit_balance":       balance,
 			"low_credit_threshold": threshold,
 			"billing_mode":         billingMode,
+			"last_used":            lastUsed,
+			"models":               models,
 		})
 	}