fix(multi): resolve 14 bugs from second comprehensive review

Core (solitaire_core):
- fix(scoring): apply -15 penalty for Foundation→Tableau moves when
  take_from_foundation is enabled; update test
- fix(solver): is_won() validates full Ace→King suit sequence, not
  just card count — prevents hint system from emitting invalid paths

Engine — animation / layout:
- fix(animation): guard CardAnim advance against duration=0 to prevent
  NaN-poisoned Transform (analogous to CardAnimation's instant-snap path)
- fix(card_plugin): align TABLEAU_FAN_FRAC (0.25→0.18) and
  TABLEAU_FACEDOWN_FAN_FRAC (0.20→0.14) with layout.rs so the initial
  layout and first dynamic update produce identical fan spacing
- fix(layout): update tableau_fan_frac doc comment from 0.25→0.18

Engine — ECS / modal guards:
- fix(auto_complete): drive_auto_complete now checks PausedResource so
  cooldown does not tick while paused (prevents instant-move on unpause)
- fix(play_by_seed): handle_open_dialog checks global ModalScrim guard
  to prevent stacking over an existing modal
- fix(win_summary): spawn_win_summary_after_delay checks global
  ModalScrim guard; collect_session_achievements uses .next() not
  .last() to avoid draining the new_games stream

Engine — message registration:
- fix(leaderboard): register InfoToastEvent in LeaderboardPlugin::build
  so opt-in/opt-out toasts work under MinimalPlugins
- fix(replay_playback): register StateChangedEvent in
  ReplayPlaybackPlugin::build to prevent panic when used standalone

Security:
- fix(sync_setup): zero password SyncFieldBuffer immediately after
  spawning auth task — credential must not linger in ECS components

Server:
- fix(auth): replace MIME contains-chain with exact match for avatar
  upload; removes illusory starts_with guard and dead ALLOWED_IMAGE_TYPES

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

solitaire_core/src/scoring.rs

@@ -9,9 +9,11 @@ use crate::pile::PileType;
 pub fn score_move(from: &PileType, to: &PileType) -> i32 {
     match to {
         PileType::Foundation(_) => 10,
-        PileType::Tableau(_) => {
-            if matches!(from, PileType::Waste) { 5 } else { 0 }
-        }
+        PileType::Tableau(_) => match from {
+            PileType::Waste => 5,
+            PileType::Foundation(_) => -15,
+            _ => 0,
+        },
         _ => 0,
     }
 }
@@ -71,13 +73,12 @@ mod tests {
     }
 
     #[test]
-    fn non_waste_to_tableau_scores_zero() {
-        // Foundation → Tableau is impossible in practice but must score 0.
-        assert_eq!(score_move(&PileType::Foundation(0), &PileType::Tableau(0)), 0);
-        // Tableau → Tableau (restack) scores 0.
-        assert_eq!(score_move(&PileType::Tableau(1), &PileType::Tableau(2)), 0);
+    fn foundation_to_tableau_penalises_fifteen() {
+        // Moving a card back off a foundation (take_from_foundation rule) costs -15.
+        assert_eq!(score_move(&PileType::Foundation(0), &PileType::Tableau(0)), -15);
     }
 
+
     #[test]
     fn move_to_stock_or_waste_scores_zero() {
         // These destinations are illegal moves in practice, but the function