Fix crash when extra_usage fields are null

ClaudeChecker/Models.swift

@@ -83,10 +83,10 @@ struct UsageWindow: Codable {
 
 struct ExtraUsage: Codable {
     let isEnabled: Bool
-    let monthlyLimit: Double
-    let usedCredits: Double
-    let utilization: Double
-    let currency: String
+    let monthlyLimit: Double?
+    let usedCredits: Double?
+    let utilization: Double?
+    let currency: String?
     enum CodingKeys: String, CodingKey {
         case isEnabled = "is_enabled"
         case monthlyLimit = "monthly_limit"
@@ -94,6 +94,14 @@ struct ExtraUsage: Codable {
         case utilization
         case currency
     }
+    init(from decoder: Decoder) throws {
+        let c = try decoder.container(keyedBy: CodingKeys.self)
+        isEnabled    = (try? c.decodeIfPresent(Bool.self,   forKey: .isEnabled)) ?? false
+        monthlyLimit = try? c.decodeIfPresent(Double.self,  forKey: .monthlyLimit)
+        usedCredits  = try? c.decodeIfPresent(Double.self,  forKey: .usedCredits)
+        utilization  = try? c.decodeIfPresent(Double.self,  forKey: .utilization)
+        currency     = try? c.decodeIfPresent(String.self,  forKey: .currency)
+    }
 }
 
 // (Bootstrap models removed — org ID is configured directly)