fix(phase-4): add DB error checking, mask sensitive auth tokens in API and middleware logs

internal/middleware/auth.go

@@ -72,7 +72,11 @@ func AuthMiddleware(database *db.DB, requireAuth bool) gin.HandlerFunc {
 
 			c.Next()
 		} else {
-			log.Printf("Token not found, inactive or error in DB: %s (err: %v)", token, err)
+			maskedToken := "••••"
+			if len(token) > 8 {
+				maskedToken = token[:3] + "••••" + token[len(token)-4:]
+			}
+			log.Printf("Token not found, inactive or error in DB: %s (err: %v)", maskedToken, err)
 			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
 				"error": gin.H{
 					"message": "Invalid or inactive client token.",