Migrate pre-commit hooks from pre-commit to prek

Replace the Python-based pre-commit framework with prek (Rust) for
faster hook execution. Convert .pre-commit-config.yaml to prek.toml,
remove pre-commit from dev dependencies, and apply ruff auto-fixes
(UP037: remove unnecessary string quotes in type annotations).

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

backend/src/app/models/boss_result.py

@@ -23,8 +23,8 @@ class BossResult(Base):
     attempts: Mapped[int] = mapped_column(SmallInteger, default=1)
     completed_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
 
-    run: Mapped["NuzlockeRun"] = relationship(back_populates="boss_results")
-    boss_battle: Mapped["BossBattle"] = relationship()
+    run: Mapped[NuzlockeRun] = relationship(back_populates="boss_results")
+    boss_battle: Mapped[BossBattle] = relationship()
 
     def __repr__(self) -> str:
         return f"<BossResult(id={self.id}, run_id={self.run_id}, boss_battle_id={self.boss_battle_id}, result='{self.result}')>"