feat: add prisma schema and migrations to rebuild triggers

Ensures branch switches with schema changes re-run the install step
and apply migrations automatically.

Author: dahyman91

Coastfile

@@ -76,6 +76,6 @@ backend = "hot"
 zoekt = "none"
 
 [assign.rebuild_triggers]
-web = ["package.json", "yarn.lock"]
-backend = ["package.json", "yarn.lock"]
+web = ["package.json", "yarn.lock", "packages/db/prisma/schema.prisma", "packages/db/prisma/migrations"]
+backend = ["package.json", "yarn.lock", "packages/db/prisma/schema.prisma", "packages/db/prisma/migrations"]
 zoekt = ["vendor/zoekt"]