fix: refresh roster data before validation to prevent stale cache

TransactionBuilder cached roster data indefinitely via _roster_loaded flag,
causing validation to use stale counts when builders persisted across multiple
/ilmove invocations. Now validate_transaction() always fetches fresh roster
data. Also adds dependency injection for roster_service to improve testability.

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

services/transaction_builder.py

@@ -174,7 +174,13 @@ class RosterValidationResult:
 class TransactionBuilder:
     """Interactive transaction builder for complex multi-move transactions."""
 
-    def __init__(self, team: Team, user_id: int, season: int = get_config().sba_season):
+    def __init__(
+        self,
+        team: Team,
+        user_id: int,
+        season: int = get_config().sba_season,
+        roster_svc=None,
+    ):
         """
         Initialize transaction builder.
 
@@ -182,12 +188,14 @@ class TransactionBuilder:
             team: Team making the transaction
             user_id: Discord user ID of the GM
             season: Season number
+            roster_svc: RosterService instance (defaults to global roster_service)
         """
         self.team = team
         self.user_id = user_id
         self.season = season
         self.moves: List[TransactionMove] = []
         self.created_at = datetime.now(timezone.utc)
+        self._roster_svc = roster_svc or roster_service
 
         # Cache for roster data
         self._current_roster: Optional[TeamRoster] = None
@@ -201,13 +209,19 @@ class TransactionBuilder:
             f"TransactionBuilder initialized for {team.abbrev} by user {user_id}"
         )
 
-    async def load_roster_data(self) -> None:
-        """Load current roster data for the team."""
-        if self._roster_loaded:
+    async def load_roster_data(self, force_refresh: bool = False) -> None:
+        """Load current roster data for the team.
+
+        Args:
+            force_refresh: If True, bypass cache and fetch fresh data from API.
+        """
+        if self._roster_loaded and not force_refresh:
             return
 
         try:
-            self._current_roster = await roster_service.get_current_roster(self.team.id)
+            self._current_roster = await self._roster_svc.get_current_roster(
+                self.team.id
+            )
             self._roster_loaded = True
             logger.debug(f"Loaded roster data for team {self.team.abbrev}")
         except Exception as e:
@@ -353,7 +367,9 @@ class TransactionBuilder:
         Returns:
             RosterValidationResult with validation details
         """
-        await self.load_roster_data()
+        # Always refresh roster data before validation to prevent stale cache
+        # from causing incorrect roster counts (e.g. after a previous /ilmove submission)
+        await self.load_roster_data(force_refresh=True)
 
         # Load existing transactions if next_week is provided
         if next_week is not None: