HFI Station Admin: Order stations in planning area

**As a** *HFI Admin* **I want** *change the order of stations in a planning area* **So That** *the order matches the operational expectations*

**Additional Context**
- `PlanningWeatherStation` model
- [FIGMA](https://www.figma.com/file/FReMPNBDzxYeE8hlxRvsoB/HFI-Calc-(Prepski)-2022?node-id=1473%3A5133)
- User permission required: station_admin

**Acceptance Criteria**
- [ ] Given I'm administrating stations, When I change the order of stations in a planning area (in the station admin modal), Then that order is reflected in the PDF and HFI calculator

**Definition of Done**
- Ready to Demo in Sprint Review
- Does what I have made have appropriate test coverage?
- Documentation and/or scientific documentation exists and can be found
- Peer Reviewed by 2 people on the team
- Manual testing of all PRs in Dev and Prod
- Merged

Start by tracing the PlanningWeatherStation model and the station admin modal described in the issue, then identify how station order reaches the PDF and HFI calculator. Use the linked Figma design for the intended admin experience. Done means an HFI Admin can reorder stations in a planning area and that order is reflected in both outputs, with appropriate test coverage.

Written by the indexing model from the issue text.