fix: send auth token with sentence boundary API requests

ios/OralTrainer/Services/SentenceBoundaryAPI.swift

@@ -20,11 +20,16 @@ enum SentenceBoundaryAPI {
         guard hash.range(of: AppConfig.sha256Pattern, options: .regularExpression) != nil else {
             throw SentenceBoundaryAPIError.invalidHash
         }
+        var headers: [String: String] = [:]
+        if !AppConfig.authToken.isEmpty {
+            headers["Authorization"] = "Bearer \(AppConfig.authToken)"
+        }
         let result = try await HTTPClient.getJSON(
             SentenceBoundaryDocument.self,
             baseURL: AppConfig.serverBaseURL,
             path: "api/v1/videos/\(hash)/sentence-boundaries",
-            timeout: AppConfig.readTimeout
+            timeout: AppConfig.readTimeout,
+            additionalHeaders: headers
         )
         guard result.value.videoHash.lowercased() == hash else {
             throw SentenceBoundaryAPIError.hashMismatch