Add representative week/two-week test fixture for days_per_period config path

[coderabbitai]

Summary

All current test configs pin days_per_period to 365, which means the new config-driven seasonal/storage/ramping scaling logic introduced in #264 is only exercised at a single value.

Task

Add at least one test database fixture that uses a non-365 value for days_per_period (e.g., 7 for a representative week, or 14 for a representative two-week period) to catch regressions in the new config-based path.

Acceptance Criteria

• Add a new test database (SQL fixture) configured as a representative week (days_per_period = 7) and/or representative two-week period (days_per_period = 14).
• Add a corresponding test config TOML file that sets days_per_period to the non-365 value.
• Ensure existing tests continue to pass and new tests run against both the original 365-day and the new non-365 fixture.
• The fixture should specifically exercise the seasonal/storage/ramping constraint scaling logic.

Background

This was identified during the review of PR #264 (Rework the definition of seasons), in the comment: #264 (comment)

Requested by @idelder.