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/pokemon.py

@@ -15,10 +15,10 @@ class Pokemon(Base):
     types: Mapped[list[str]] = mapped_column(ARRAY(String(20)))
     sprite_url: Mapped[str | None] = mapped_column(String(500))
 
-    route_encounters: Mapped[list["RouteEncounter"]] = relationship(
+    route_encounters: Mapped[list[RouteEncounter]] = relationship(
         back_populates="pokemon"
     )
-    encounters: Mapped[list["Encounter"]] = relationship(
+    encounters: Mapped[list[Encounter]] = relationship(
         foreign_keys="[Encounter.pokemon_id]", back_populates="pokemon"
     )