feat(engine): wire AnimSpeed to animation, new achievements, leaderboard opt-in, daily goal display

- AnimSpeed setting now drives card slide duration (Normal=0.15s, Fast=0.07s, Instant=snap);
  EffectiveSlideDuration resource updated on SettingsChangedEvent; AnimSpeed row added to Settings panel
- GameState.recycle_count tracks waste recycles; perfectionist/comeback/zen_winner achievements added
  with full unit tests
- SyncProvider gains opt_in_leaderboard(); SolitaireServerClient implements POST /api/leaderboard/opt-in;
  Opt In button added to leaderboard panel
- DailyChallengeResource stores goal_description/target_score/max_time_secs from server;
  pressing C shows goal description as toast (DailyGoalAnnouncementEvent)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_data/src/lib.rs

@@ -41,6 +41,11 @@ pub trait SyncProvider: Send + Sync {
     async fn fetch_daily_challenge(&self) -> Result<Option<ChallengeGoal>, SyncError> {
         Ok(None)
     }
+    /// Opt the authenticated player into the leaderboard with the given
+    /// display name. No-op for backends that don't support leaderboards.
+    async fn opt_in_leaderboard(&self, _display_name: &str) -> Result<(), SyncError> {
+        Ok(())
+    }
 }
 
 /// Blanket impl so `Box<dyn SyncProvider + Send + Sync>` (returned by
@@ -68,6 +73,9 @@ impl SyncProvider for Box<dyn SyncProvider + Send + Sync> {
     async fn fetch_daily_challenge(&self) -> Result<Option<ChallengeGoal>, SyncError> {
         (**self).fetch_daily_challenge().await
     }
+    async fn opt_in_leaderboard(&self, display_name: &str) -> Result<(), SyncError> {
+        (**self).opt_in_leaderboard(display_name).await
+    }
 }
 
 pub mod stats;