Swap splash tiles to viz screenshots

This commit swaps the tiles used on the splash page from the previous doctored electron micrographs to be simple screenshots of the pages / pathogens that are linked to. This has two advantages:
1. It's super simple and no longer requires sourcing a copyright-free image and doctoring it in LunaPic
2. It's a more up front, more transparent window into what you get when you click on a tile

I used tree vs map depending on spatial / epi patterns. For pathogens like WNV and Ebola, the map is meaningful and interesting, while for things like H3N2, it's less relevant. I generally tried to stick close to the content that's directly linked and not update coloring, etc..., but I made a couple of exceptions for visual interest.

static-site/src/components/Cards/styles.tsx

@@ -2,8 +2,6 @@ import styled from "styled-components";
 
 export const CardImg = styled.img`
   object-fit: contain;
-  border-radius: 6px;
-  box-shadow: 3px 3px 3px 1px rgba(0, 0, 0, 0.15);
   max-height: 100%;
   width: 100%;
   background-color: ${(props) => props.color};

static-site/src/components/splash/showcase.yaml

@@ -1,37 +1,37 @@
 cards:
 - name: SARS-CoV-2
-  img: ncov.png
+  img: ncov_tree.png
   url: /ncov/
 - name: H5N1 cattle outbreak
-  img: avianinfluenza.png
+  img: h5n1_cattle_outbreak_tree.png
   url: /avian-flu/h5n1-cattle-outbreak/genome
 - name: avian influenza
-  img: avianinfluenza.png
+  img: h5n1_map.png
   url: /avian-flu/h5n1/ha/2y
 - name: mpox
-  img: mpox.png
+  img: mpox_tree.png
   url: /mpox/clade-IIb
 - name: Ebola in the DRC
-  img: ebola2.png
+  img: ebola_drc_map.png
   url: /community/inrb-drc/ebola-nord-kivu
 - name: measles
-  img: measles.jpg
+  img: measles_tree.png
   url: /measles/N450
 - name: seasonal influenza
-  img: seasonalinfluenza.png
+  img: h3n2_tree.png
   url: /seasonal-flu
 - name: RSV
-  img: rsv1.png
+  img: rsv_tree.png
   url: /rsv
 - name: Yersinia pestis
-  img: yersinia.png
+  img: yersinia_tree.png
   url: /community/ktmeaton/yersinia-pestis/maximum-likelihood/all?m=div
 - name: WNV in the Americas (narrative)
-  img: wnv2.png
+  img: wnv_map.png
   url: /narratives/twenty-years-of-WNV
 - name: Chikungunya
-  img: chikv.png
+  img: chikv_map.png
   url: /groups/ViennaRNA/CHIKVnext
 - name: HIV
-  img: hiv_community.png
+  img: hiv_tree.png
   url: /groups/LANL-HIV-DB/HIV/env