feat: implement Stripe product configuration and add token-based input validation using Microsoft.ML.Tokenizers

src/NexusReader.Infrastructure/Configuration/AiSettings.cs

@@ -6,7 +6,12 @@ public class AiSettings
 
     public string ApiKey { get; set; } = string.Empty;
     public string Model { get; set; } = "gemini-1.5-flash";
-    public int MaxInputLength { get; set; } = 15000;
+    
+    /// <summary>
+    /// Maximum number of tokens allowed for input.
+    /// </summary>
+    public int MaxInputTokens { get; set; } = 15000;
+    
     public int MaxOutputTokens { get; set; } = 1000;
     public int RetryAttempts { get; set; } = 3;
     public double Temperature { get; set; } = 0.1;

src/NexusReader.Infrastructure/Configuration/StripeSettings.cs

@@ -0,0 +1,9 @@
+namespace NexusReader.Infrastructure.Configuration;
+
+public record StripeSettings
+{
+    public const string SectionName = "Stripe";
+    public string ProProductId { get; init; } = string.Empty;
+    public string BasicProductId { get; init; } = string.Empty;
+    public string FreeProductId { get; init; } = string.Empty;
+}