Drop redundant exception interpolation in `logger.exception(...)` calls

[nanotaboada]

Problem

services/player_service.py logs caught exceptions like this (three
occurrences, in create_async, update_by_squad_number_async,
delete_by_squad_number_async):

except SQLAlchemyError as error:
    logger.exception("Error trying to create the Player: %s", error)
    await async_session.rollback()

Logger.exception() already attaches the active exception — type, message, and
full traceback — to the log record. Interpolating error with %s duplicates
the message text and adds noise. The idiomatic call passes only the static
message.

Proposed Solution

except SQLAlchemyError:
    logger.exception("Error trying to create the Player")
    await async_session.rollback()
    return None

The logger.error("Player not found for update: squad_number=%s", squad_number) calls are correct as-is — there is no active exception
there, and they interpolate data, not an exception.

Suggested Approach

1. In each except SQLAlchemyError as error: block that calls
   logger.exception(...), drop the as error binding and the : %s /
   , error argument.
2. Leave the logger.error(...) data-interpolation calls untouched.
3. tools/seed_*.py has the same logger.exception("...: %s", exc) pattern —
   fix there too if convenient (lower priority; tools/ is legacy).
4. Run uv run pytest.

Acceptance Criteria

• logger.exception() calls carry a static message, no exception %s
• Unused as error bindings removed
• logger.error(...) data-interpolation calls unchanged
• All tests pass
• CHANGELOG.md updated

References

• logging.Logger.exception
• Logging HOWTO — exceptions