fix(engine): resolve all clippy warnings introduced by PNG asset pipeline

- Collapse nested-if patterns into let-chains across 13 plugins (42 instances)
- Add #[allow(clippy::too_many_arguments)] to 5 Bevy systems in card_plugin
  and input_plugin where ECS parameter count exceeds the lint threshold
- Gate Theme import in table_plugin under #[cfg(test)] — only used by
  test-only colour helpers; removing the unconditional import silences the
  unused-import lint without breaking the test suite
- Wrap ButtonInput<MouseButton> in Option<> in update_input_platform so that
  tests using MinimalPlugins (no InputPlugin) no longer panic on startup

All 789 tests pass; cargo clippy --workspace -- -D warnings is clean.

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

solitaire_engine/src/daily_challenge_plugin.rs

@@ -161,27 +161,24 @@ fn handle_daily_completion(
             continue;
         }
         // Enforce server-supplied goal constraints when present.
-        if let Some(target) = daily.target_score {
-            if ev.score < target {
+        if let Some(target) = daily.target_score
+            && ev.score < target {
                 continue; // score goal not met
             }
-        }
-        if let Some(max_secs) = daily.max_time_secs {
-            if ev.time_seconds > max_secs {
+        if let Some(max_secs) = daily.max_time_secs
+            && ev.time_seconds > max_secs {
                 continue; // time limit exceeded
             }
-        }
         if !progress.0.record_daily_completion(daily.date) {
             // Already counted today — no-op.
             continue;
         }
         progress.0.add_xp(DAILY_BONUS_XP);
         xp_awarded.write(XpAwardedEvent { amount: DAILY_BONUS_XP });
-        if let Some(target) = &path.0 {
-            if let Err(e) = save_progress_to(target, &progress.0) {
+        if let Some(target) = &path.0
+            && let Err(e) = save_progress_to(target, &progress.0) {
                 warn!("failed to save progress after daily completion: {e}");
             }
-        }
         completed.write(DailyChallengeCompletedEvent {
             date: daily.date,
             streak: progress.0.daily_challenge_streak,