Improvements and fixes

The plant activity heatmap no longer lights cells from before onboarding, and the solar segment filter no longer returns an error. A plant's timezone now follows its coordinates.

• On a plant's "Activity" page, the heatmap no longer lights cells from before the plant was onboarded.
• On a plant's solar strings and generator connection point lists, the segment filter no longer returns an error.
• Onboarding a data logger whose account still has its initial password now explains the one-time password change in the logger's web interface.
• A plant's timezone now follows its coordinates when the plant is created or its coordinates change.