Remove hub-specific keywords in URL date params

[emprzy]

Currently:

• https://staging.respilens.com/forecasts/flusight?flu_dates=2026-05-23
• https://staging.respilens.com/forecasts/flusight/peak?flu_dates=2026-05-23
• https://staging.respilens.com/forecasts/flu-metrocast?metrocast_dates=2026-05-16%2C2026-05-23
• https://staging.respilens.com/forecasts/rsv/CO?rsv_dates=2026-05-30
• https://staging.respilens.com/forecasts/covid/CO?covid_dates=2026-08-22

Joseph's wish is to remove the hub-specific word from the param, and instead have a catchall ?dates=... param. Need to change the files necessary to actually execute this shift, and then also examine+change extractPlotDataFromURL.js, and any knock-on effects with MyPlots.jsx/MiniPlot.jsx.

[jcblemai]

if too hard/too downstream, not too hang up on that