refactor(audience-sdk): name consent-sync retry budgets

Replaces the inline 4-attempt cap and 1-second base retry on the consent-sync PUT retry loop with
named constants on ImmutableAudience so the budget is visible at the top of the class and a tuning
change touches one place.

- ImmutableAudience.cs: adds ConsentSyncMaxAttempts (4) and ConsentSyncBaseRetryMs (1000).
- ImmutableAudience.cs: SyncConsentLevel uses ConsentSyncMaxAttempts and ConsentSyncBaseRetryMs in
  the 429 retry loop.

Author: ImmutableJeffrey

src/Packages/Audience/Runtime/ImmutableAudience.cs

@@ -27,6 +27,12 @@ public static class ImmutableAudience
         // teardown (Session.Dispose, timer drain, queue shutdown, transport
         // flush, disposes). This keeps the hold time to nanoseconds so a caller
         // arriving on a different thread is not stranded behind those budgets.
+        // How many times we retry the consent-sync PUT after a 429.
+        internal const int ConsentSyncMaxAttempts = 4;
+
+        // How long we wait before the first consent-sync retry. Doubles each time.
+        internal const int ConsentSyncBaseRetryMs = 1_000;
+
         private static AudienceConfig? _config;
         private static DiskStore? _store;
         private static EventQueue? _queue;
@@ -625,9 +631,9 @@ private static void SyncConsentToBackend(AudienceConfig config, ConsentLevel lev
 
             Task.Run(async () =>
             {
-                // 429 retried up to 4 attempts (1s/2s/4s or Retry-After).
-                // Other non-2xx fail fast.
-                const int maxAttempts = 4;
+                // 429 retried up to ConsentSyncMaxAttempts attempts (1s/2s/4s
+                // or Retry-After). Other non-2xx fail fast.
+                const int maxAttempts = ConsentSyncMaxAttempts;
                 var attempt = 0;
                 try
                 {
@@ -644,7 +650,7 @@ private static void SyncConsentToBackend(AudienceConfig config, ConsentLevel lev
                         if (response.StatusCode == HttpStatusCode.TooManyRequests && attempt < maxAttempts)
                         {
                             var delay = HttpRetry.ParseRetryAfter(response)
-                                ?? TimeSpan.FromMilliseconds(1_000 * (1 << (attempt - 1)));
+                                ?? TimeSpan.FromMilliseconds(ConsentSyncBaseRetryMs * (1 << (attempt - 1)));
                             await Task.Delay(delay, cancellationToken).ConfigureAwait(false);
                             continue;
                         }