Closes#113
Adds a specific `DoesNotExist` handler before the generic `Exception`
block in `update_game_season_stats`. Peewee's `DoesNotExist` (raised
when `StratGame.get_by_id(game_id)` finds no row) previously bubbled
through to the `except Exception` handler which included raw SQL and
params in the 500 detail string. Now returns a clean 404.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>