chore(deps): migrate to Bevy 0.16, axum 0.8, and other package updates

- Bump bevy 0.15 → 0.16; fixes all breaking API changes:
  ChildBuilder → ChildSpawnerCommands, Parent → ChildOf,
  despawn_descendants → despawn_related::<Children>(),
  despawn_recursive → despawn (now recursive by default),
  EventWriter::send → write, Query::{get_single,get_single_mut}
  → {single,single_mut}, ChildOf::get → parent()
- Bump axum 0.7 → 0.8; remove axum::async_trait from FromRequestParts
- Bump tower_governor 0.4 → 0.8; fix GovernorLayer::new() API
- Bump jsonwebtoken 9 → 10 with rust_crypto feature only
- Bump thiserror 1 → 2, dirs 5 → 6, bcrypt 0.15 → 0.19,
  reqwest 0.12 → 0.13 (rustls feature rename)
- Regenerate .sqlx offline cache for sqlx compile-time query checks

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

solitaire_engine/src/weekly_goals_plugin.rs

@@ -92,7 +92,7 @@ fn evaluate_weekly_goals(
             any_change = true;
             if just_completed {
                 bonus_xp = bonus_xp.saturating_add(WEEKLY_GOAL_XP);
-                completions.send(WeeklyGoalCompletedEvent {
+                completions.write(WeeklyGoalCompletedEvent {
                     goal_id: def.id.to_string(),
                     description: def.description.to_string(),
                 });
@@ -101,10 +101,10 @@ fn evaluate_weekly_goals(
     }
 
     if bonus_xp > 0 {
-        xp_awarded.send(XpAwardedEvent { amount: bonus_xp });
+        xp_awarded.write(XpAwardedEvent { amount: bonus_xp });
         let prev_level = progress.0.add_xp(bonus_xp);
         if progress.0.leveled_up_from(prev_level) {
-            levelups.send(LevelUpEvent {
+            levelups.write(LevelUpEvent {
                 previous_level: prev_level,
                 new_level: progress.0.level,
                 total_xp: progress.0.total_xp,