HFI Calculator: Load times waaay too slow 🐢

**As a** *user, any user, ever* **I want** *web products to load as quickly as possible* **So That** *I can achieve my goals, complete my tasks, feel confident in the product(s) I am using for critical operations decisions, and have a good digital experience*

**Additional Context**
- Waiting is frustrating - especially given time is of the essence when folks are using these operations tools (busy fire season, deadline to analyze, make decisions, and disseminate this information to the right people).
- Friction due to load times can detract from a users perception of our product(s) and may impact their task success
- How might we create a standard or acceptable benchmark? A standard we test all of our products against.
- Generally a web best practice is 1-2 seconds, faster is _always_ better.

**Acceptance Criteria**
- [ ] Given I open the HFI Calculator, The page and table data loads as quickly as possible, 2 seconds or faster
- [ ] Given I switch views (e.g. weekly to daily or date change), The new page / table data loads as quickly as possible, 2 seconds or faster
- [ ] Given I open the HFI Calculator for the first time or switch views (e.g. weekly to daily or date change), I see a spinning icon / loading indicator
- [ ] Given I make a change in the HFI Calculator (future input fields), When the applicable table data is recalculated, Then table data loads as quickly as possible, 2 seconds or faster
- [ ] Given I make a change in the HFI Calculator (future input fields), When the applicable table data is recalculated, Then the affected row(s) display a loading-shimmer effect

**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 locating the HFI Calculator entry point and measuring initial loads and view switches such as weekly-to-daily or date changes. Review the page and table-data loading paths, then define the loading indicator and row shimmer behavior. Done means the listed interactions meet the 2-second target and have appropriate test coverage and documentation.

Written by the indexing model from the issue text.