Move the use-case index onto Learn so the pilot stories stay reachable, and make share images resolve on the host that serves the page.

Co-authored-by: Cursor <cursoragent@cursor.com>

messages/en/pages/useCases.json

@@ -5,7 +5,7 @@
   "caseStudyTiles": {
     "mutualAidColoradoAlt": "Mutual Aid Colorado logo",
     "foodNotBombsAlt": "Food Not Bombs logo",
-    "boulderCountyStreetMedicsAlt": "Boulder County Street Medics logo",
+    "boulderCountyStreetMedicsAlt": "Boulder Street Medics logo",
     "links": [
       {
         "href": "/use-cases/mutual-aid-colorado",
@@ -17,7 +17,7 @@
       },
       {
         "href": "/use-cases/boulder-county-street-medics",
-        "ariaLabel": "View Boulder County Street Medics use case"
+        "ariaLabel": "View Boulder Street Medics use case"
       }
     ]
   },